**Determination of Chemical State and External Magnetic Field Effect on the Energy Shifts and X-Ray Intensity Ratios of Yttrium and Its Compounds**

Sevil Porikli1 and Yakup Kurucu2

*Erzincan University, Faculty of Art and Sciences, Department of Physics Atatürk University, Faculty of Sciences, Department of Physics Turkey* 

#### **1. Introduction**

88 Radioisotopes – Applications in Physical Sciences

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The term 'X-ray fluorescence analysis' (XRF) refers to the measurement of characteristic fluorescent emission resulting from the deexcitation of inner shell vacancies produced in the sample by means of a suitable source of radiation. For a particular energy (wavelength) of fluorescent light emitted by a sample, the number of photons per unit time (generally referred to as peak intensity or count rate) is related to the amount of that analyte in the sample. The counting rates for all detectable elements within a sample are usually calculated by counting, for a set amount of time, the number of photons that are detected for the various analytes' characteristic X-ray energy lines. It is important to note that these fluorescent lines are actually observed as peaks with a semi-Gaussian distribution because of the imperfect resolution of modern detector technology. Therefore, by determining the energy of the X-ray peaks in a sample's spectrum, and by calculating the count rate of the various elemental peaks, it is possible to qualitatively establish the elemental composition of the samples and to quantitatively measure the concentration of these elements.

XRF is an analytical method to determine the chemical composition of all kinds of materials. The materials can be in solid, liquid, powder, filtered or other form. XRF can also sometimes be used to determine the thickness and composition of layers and coatings. The method is fast, accurate and non-destructive, and usually requires only a minimum of sample preparation. Applications are very broad and include the metal, cement, oil, polymer, plastic and food industries, along with mining, mineralogy and geology, and environmental analysis is of water and waste materials. XRF is also a very useful analysis technique for research and pharmacy.

For routine XRF analysis, two major approaches are distinguishable based on the type of detector used to measure the characteristic X-ray emission spectra. Wavelength dispersive X-ray fluorescence (WDXRF) analyses depend upon the use of diffracting crystal to determine the characteristic wavelength of the emitted X-rays. Energy dispersive X-ray fluorescence (EDXRF) employs detectors that directly measure the energy of the X-rays by collecting the ionization produced in suitable detecting medium.

Determination of Chemical State and External Magnetic Field

compounds for *Kβ*1,3 and *Kβ*2 components.

experimental support.

configuration.

Effect on the Energy Shifts and X-Ray Intensity Ratios of Yttrium and Its Compounds 91

electron configuration. Although some investigations have been made to study their electronic structures individually, no systematic study has been made so far for understanding the valence electronic structure of all the 3*d* transition metals. With a deeper theoretical understanding of the underlying processes and further improving X-ray sources, sophisticated experiments have been developed (e.g., resonant inelastic scattering, magnetic dichroism (Groot, 1994a,b)) that give detailed information on the valance electron

In a number of X-ray spectral studies of 3*d* transition metals it has been observed that the *Kβ*-to-*Kα* X-ray intensity ratios are dependent on the physical and chemical environments of the elements in the sample. In the earlier studies of 3*d* metal compounds (Küçüköder et al., 1993; Padhi et al., 1993, 1995), the influence of chemical effects has shown difference in the *Kβ*-to-*Kα* X-ray intensity ratios up to nearly 10%. Such chemical effects can be caused either by a varying 3*d* electron population or by the admixture of *p* states from the ligand atoms to the 3*d* states of the metal or both. Brunner et al. (1982) explained their experimental results by the change in screening of 3*p* electron by 3*d* valance electrons as well as the polarization effect. They also pointed out that the chemical effect is almost the same order of magnitude as the effect of excitation mode and both effects should be studied separately. However, most of these measurements have been performed with solid-state X-ray detectors and the change in the satellite peaks in the *Kβ* X-ray region has not been studied because of poor energy resolution. Urch (1979) discussed the chemical effect on the *K* X-ray spectra based on molecular-orbital (MO) theory. Similar studies on the chemical effect on the X-ray spectra have already been done extensively. However, these studies are concerned mostly on with transition energies and profiles of X-rays, and qualitative discussions on the intensities have not yet been made. Tamaki et al. (1979) studied Cr and 55Mn-labeled compounds and reported that the *Kβ*/*Kα* ratio increases with increasing formal oxidation number of the element in the compound. Kataria et al. (1986) found deviations of up to 10% for the same ratio in the case of Mn compounds. Mukoyama et al. (1986) experimentally confirmed the theoretical predictions following Brunners' (1982) model in the case of Te and Mo

Wide employed applications and the intriguing asymmetry of the Cu Kα and Kβ line shapes (Deutsch&Hart, 1982) along with those of all 3d transition elements, led in turn to a century of extensive spectrometric studies of the Cu *Kα* and *Kβ* spectra. In spite of these extensive studied, recent studies reveal that surprises still lurk under the skewed *Kα*1,2 and overlapping *Kβ*1,3 lines, and the related multi-electronic satellite (S) and hypersatellite (HS) spectra. The asymmetric lineshape of the copper emission lines were attributed in the past to a number of different processes: Kondo-like interaction of the conduction electrons with the core holes, final state interactions between the core holes and the incomplete 3*d* shell, 2*p*/3*d* shell electrostatic exchange interaction, and most importantly, shake-up and shake-off of electrons from the 3*l* shells. The last process, in particular, received in the past strong

Raj et al. (1998) were carried studies on CrB, CrB2 and FeB forms in order to look into the electronic structure of the transition metals in monoborides and diborides. In order to understand the valence electronic structure of the transition metals in the compounds, they have tried to compare the measured *Kβ*-to-*Kα* ratios with the multiconfiguration Dirac±Fock calculations assuming different electronic configurations for the transition metal. Such a comparison would provide information on the valence electronic structure of the transition metals in the compounds, which could in turn provide information on

X-ray emission spectra are known to be influenced by chemical combination of X-ray emitting atoms with different ligands. The effect of the chemical combination, however are not large and a theoretical interpretation of these effects has not been established completely. Therefore, chemical effects have rarely been utilized in the characterization of materials. The purpose of this work was to study chemical effects and discuss their applications to Yttrium (Y) in various compounds. So much so that, this paper presents and discusses the measured spectra both energy dispersive and wave-length dispersive X-ray spectrometer. In the first part of the study, the effect of the 0.6T and 1.2T external magnetic field and chemical state on the *Kα*, *Kβ*1,3 and *Kβ*2,4 X-ray energies and relative intensity ratios for Y, YBr3, YCl3, YF3, Y(NO3)3.6H2O, Y2O3, YPO4, Y(SO4)3.8H2O and Y2S3 have been investigated, using the 22.69 keV X-rays from a 109Cd and 59.54 keV γ-ray from a 241Am as photon sources. The measurements were done using an energy dispersive Si(Li) detector with photon excitation by radioisotopes. For B=0, the present experimental results were compared with the experimental and theoretical data in the literature.

The results show that Y2O3, YF3 and Y2S3 can change owing to the applied magnetic field. In addition, we found that the energy of characteristic X-ray series is totally independent of the excitation source and mode. However, changes have been observed in X-ray spectra when the element studied in the sample is chemically bonded to others. The development of high resolution spectrometers allows for the characterization and study of these effects.

In the second part of the study, energies and full width at half maximum (FWHM) values of the *Kα*, *Kβ*1,3 and *Kβ*2,4 X-ray of Y and its compounds were measured by a wavelength dispersive spectrometer. An accurate analytical representation of each line, obtained by a fit to a minimal set of Gaussians, is presented. The absolute energies and FWHM values derived from the data, agree well with previous measurements. Possible origins of chemical shifts are discussed. It was found that the chemical shifts of Y *Kα* line in pure Y and its some compounds relatively small (less than 0.1 eV with pure Y as reference). The influence of crystal symmetry on the energy shifts of X-ray lines is an interesting aspect of our study. The results demonstrate a clear dependence of the energy shifts on the chemical state of the element in the sample. The relative intensities are more susceptible to the chemical environment than the energy shifts.

It is well known that the chemical environment of an element affects and modifies the various characteristics of its X-ray emission spectrum. Most of the works suffer from neglecting chemical influences, and usually theoretical atomic values (Scofield, 1974a, 1974b) are used as a reference even for quite different chemical compounds of certain element. However, some papers deal with chemical effects (Berenyi et al., 1978; Rao et al., 1986), mostly in connection with X-ray emission after an electron capture process (EC) and partially after photoionisation (PI). Paic &Pecar (1976) found that for first-row transition elements the *Kβ*/*Kα* ratio depends on the mode of excitation. The difference between the ratios for electron-capture decay and photoionization becomes almost 10%. Similar results were obtained by Arndt et al., (1982) and they pointed out that the difference comes from a strong shake-off process accompanying photoionization.

The 3*d* transition metals have played an important role in the development of modern technology, and knowledge of their valence electronic structure is very important for understanding their physical properties. X-ray spectroscopy is an established tool for probing the electronic structure of 3*d* transition metal compounds (Meisel et al., 1989). A number of techniques, such as photoemission spectroscopy, X-ray absorption and X-ray emission spectroscopy create a hole in an inner shell in order to investigate the valance

X-ray emission spectra are known to be influenced by chemical combination of X-ray emitting atoms with different ligands. The effect of the chemical combination, however are not large and a theoretical interpretation of these effects has not been established completely. Therefore, chemical effects have rarely been utilized in the characterization of materials. The purpose of this work was to study chemical effects and discuss their applications to Yttrium (Y) in various compounds. So much so that, this paper presents and discusses the measured spectra both energy dispersive and wave-length dispersive X-ray spectrometer. In the first part of the study, the effect of the 0.6T and 1.2T external magnetic field and chemical state on the *Kα*, *Kβ*1,3 and *Kβ*2,4 X-ray energies and relative intensity ratios for Y, YBr3, YCl3, YF3, Y(NO3)3.6H2O, Y2O3, YPO4, Y(SO4)3.8H2O and Y2S3 have been investigated, using the 22.69 keV X-rays from a 109Cd and 59.54 keV γ-ray from a 241Am as photon sources. The measurements were done using an energy dispersive Si(Li) detector with photon excitation by radioisotopes. For B=0, the present experimental results were

The results show that Y2O3, YF3 and Y2S3 can change owing to the applied magnetic field. In addition, we found that the energy of characteristic X-ray series is totally independent of the excitation source and mode. However, changes have been observed in X-ray spectra when the element studied in the sample is chemically bonded to others. The development of high

In the second part of the study, energies and full width at half maximum (FWHM) values of the *Kα*, *Kβ*1,3 and *Kβ*2,4 X-ray of Y and its compounds were measured by a wavelength dispersive spectrometer. An accurate analytical representation of each line, obtained by a fit to a minimal set of Gaussians, is presented. The absolute energies and FWHM values derived from the data, agree well with previous measurements. Possible origins of chemical shifts are discussed. It was found that the chemical shifts of Y *Kα* line in pure Y and its some compounds relatively small (less than 0.1 eV with pure Y as reference). The influence of crystal symmetry on the energy shifts of X-ray lines is an interesting aspect of our study. The results demonstrate a clear dependence of the energy shifts on the chemical state of the element in the sample. The relative intensities are more susceptible to the chemical

It is well known that the chemical environment of an element affects and modifies the various characteristics of its X-ray emission spectrum. Most of the works suffer from neglecting chemical influences, and usually theoretical atomic values (Scofield, 1974a, 1974b) are used as a reference even for quite different chemical compounds of certain element. However, some papers deal with chemical effects (Berenyi et al., 1978; Rao et al., 1986), mostly in connection with X-ray emission after an electron capture process (EC) and partially after photoionisation (PI). Paic &Pecar (1976) found that for first-row transition elements the *Kβ*/*Kα* ratio depends on the mode of excitation. The difference between the ratios for electron-capture decay and photoionization becomes almost 10%. Similar results were obtained by Arndt et al., (1982) and they pointed out that the difference comes from a

The 3*d* transition metals have played an important role in the development of modern technology, and knowledge of their valence electronic structure is very important for understanding their physical properties. X-ray spectroscopy is an established tool for probing the electronic structure of 3*d* transition metal compounds (Meisel et al., 1989). A number of techniques, such as photoemission spectroscopy, X-ray absorption and X-ray emission spectroscopy create a hole in an inner shell in order to investigate the valance

resolution spectrometers allows for the characterization and study of these effects.

compared with the experimental and theoretical data in the literature.

environment than the energy shifts.

strong shake-off process accompanying photoionization.

electron configuration. Although some investigations have been made to study their electronic structures individually, no systematic study has been made so far for understanding the valence electronic structure of all the 3*d* transition metals. With a deeper theoretical understanding of the underlying processes and further improving X-ray sources, sophisticated experiments have been developed (e.g., resonant inelastic scattering, magnetic dichroism (Groot, 1994a,b)) that give detailed information on the valance electron configuration.

In a number of X-ray spectral studies of 3*d* transition metals it has been observed that the *Kβ*-to-*Kα* X-ray intensity ratios are dependent on the physical and chemical environments of the elements in the sample. In the earlier studies of 3*d* metal compounds (Küçüköder et al., 1993; Padhi et al., 1993, 1995), the influence of chemical effects has shown difference in the *Kβ*-to-*Kα* X-ray intensity ratios up to nearly 10%. Such chemical effects can be caused either by a varying 3*d* electron population or by the admixture of *p* states from the ligand atoms to the 3*d* states of the metal or both. Brunner et al. (1982) explained their experimental results by the change in screening of 3*p* electron by 3*d* valance electrons as well as the polarization effect. They also pointed out that the chemical effect is almost the same order of magnitude as the effect of excitation mode and both effects should be studied separately. However, most of these measurements have been performed with solid-state X-ray detectors and the change in the satellite peaks in the *Kβ* X-ray region has not been studied because of poor energy resolution. Urch (1979) discussed the chemical effect on the *K* X-ray spectra based on molecular-orbital (MO) theory. Similar studies on the chemical effect on the X-ray spectra have already been done extensively. However, these studies are concerned mostly on with transition energies and profiles of X-rays, and qualitative discussions on the intensities have not yet been made. Tamaki et al. (1979) studied Cr and 55Mn-labeled compounds and reported that the *Kβ*/*Kα* ratio increases with increasing formal oxidation number of the element in the compound. Kataria et al. (1986) found deviations of up to 10% for the same ratio in the case of Mn compounds. Mukoyama et al. (1986) experimentally confirmed the theoretical predictions following Brunners' (1982) model in the case of Te and Mo compounds for *Kβ*1,3 and *Kβ*2 components.

Wide employed applications and the intriguing asymmetry of the Cu Kα and Kβ line shapes (Deutsch&Hart, 1982) along with those of all 3d transition elements, led in turn to a century of extensive spectrometric studies of the Cu *Kα* and *Kβ* spectra. In spite of these extensive studied, recent studies reveal that surprises still lurk under the skewed *Kα*1,2 and overlapping *Kβ*1,3 lines, and the related multi-electronic satellite (S) and hypersatellite (HS) spectra. The asymmetric lineshape of the copper emission lines were attributed in the past to a number of different processes: Kondo-like interaction of the conduction electrons with the core holes, final state interactions between the core holes and the incomplete 3*d* shell, 2*p*/3*d* shell electrostatic exchange interaction, and most importantly, shake-up and shake-off of electrons from the 3*l* shells. The last process, in particular, received in the past strong experimental support.

Raj et al. (1998) were carried studies on CrB, CrB2 and FeB forms in order to look into the electronic structure of the transition metals in monoborides and diborides. In order to understand the valence electronic structure of the transition metals in the compounds, they have tried to compare the measured *Kβ*-to-*Kα* ratios with the multiconfiguration Dirac±Fock calculations assuming different electronic configurations for the transition metal. Such a comparison would provide information on the valence electronic structure of the transition metals in the compounds, which could in turn provide information on

Determination of Chemical State and External Magnetic Field

chemical environments is appreciable.

1973; Makarov, 1999; Batrakov et al., 2004).

metallic cases.

Effect on the Energy Shifts and X-Ray Intensity Ratios of Yttrium and Its Compounds 93

al. (1986) studied the variation of the relative *K* X-ray intensity ratios for compounds involving Tc isotopes, 95mTc, 97mTc and 99mTc. They found that the chemical effect on the *Kβ*/*Kα* ratios for 4*d* elements is small but the dependence of the *Kβ*2/*Kα* ratios on the

Mukoyoma et al. (1986) have calculated the *Kβ*2/*Kα* intensity ratios for chemical compounds of 4*d* transition elements by the use of the simple theoretical method of Brunner et al. (1982), originally developed for 3*d* elements. Although they obtained good agreement between theories and experimental, it was found that their model is inadequate for the

These investigations on the effect of 3*d* and 4*d* electrons were performed only to understand the chemical effect on the X-ray intensity ratios. However, if the dependence on the excitation mode is also caused by the difference in the number of 3*d* electrons, as shown in our previous work, both effects, i.e. the dependence on the chemical environment and on the excitation mode, can be treated simultaneously to estimate the *Kβ*/*Kα* ratios in terms of the number of 3*d* electrons. However it may also be possible that these ratios are also expressed as a function of other parameters, such as bond length and effective number of 4*p* electrons. Considering these facts, it is interesting to study the dependence of the *Kβ*2/*Kα*

Iiahara et al. (1993) measured the *L* X-ray intensity ratios for some Nb and Mo compounds. When the measured *Lγ*1/*Lβ*1 ratios were plotted as a function of the effective number of 4*d* electrons, they found that the experimental data are experimental data are almost on a straight line. However, it should be noted that the 4*d*→2*p* transitions are allowed dipole transition and the 4d electron is the valance shell electron which participates directly in the X-ray emission. In this case the X-ray emission rate is proportional to the number of 4*d*

The chemical behavior of actinide atoms (in particular, that of uranium) is determined by valance nl-electrons of three types: 7s, 6d and 5f. Although the bond energies of these electrons are almost equal, their wave-function differs greatly in distribution in the radial direction (Katz et al., 1986; Balasubramanian et al., 1994). It can be said that the 5f electrons have an only core arrangement in the atom. Therefore, when actinides chemical bonding is studied, several questions should be raised: (1) the possibility and form of 5f electrons participation in chemical bonding; (2) the necessity for taking into account the splitting of valance levels of the atom into two sublevels nl+ and nl- with total angular momentum j=1±1/2 because of the relativistic effect of spin-orbital splitting (SOS) (Pyykko,1988; Pepper et al., 1991); (3) the energetic stabilization of the specific chemical state of the heavy atom due to fine effects of electron density redistribution on valance orbital; (4) the possibility of independent participation of split subshells in chemical bond formation. One of the methods of modern precise spectroscopy capable of providing a correct description of chemical bonding process is the chemical shift (CS) method of X-ray emission lines, i.e. the change in their energy when the chemical state of the emitting atom is changed (Gohshi&Ohtsuka,

Atomic theory has shown that the magnetic dipole moments observed in bulk matter arise from one or two origins: one is the motion of the electrons about their atomic nucleus (orbital angular momentum) and the other is the rotation of the electron about its own axis (spin angular momentum). The nucleus itself has a magnetic moment. Except in special types of experiments, this moment is so small that it can be neglected in the consideration of the usual macroscopic magnetic properties of bulk matter. When the atom is placed in an

ratio in 3*d* elements on various parameters of chemical compounds.

electrons and increases with increasing effective number of 4*d* electrons.

the rearrangement of electrons between 3*d* and 4*s* states of the metal or electron transfer from the 3*d* state of the metal to the ligand atoms or vice-versa.

The chemical environment has a strong effect on the transitions originated in valence band and its influence could clearly be observed in the emission spectrum structure. The P-*Kβ* spectrum has been studied by many authors (Takashi, 1972; Taniguchi 1984; Torres Delluigi et al., 2003), who used both single-crystal and two-crystal spectrometers with conventional X-ray sources. These authors showed some modifications in the *Kβ* spectra and its relation with P chemical environment. Compounds with oxygen as ligand atom, a relationship between the ratio of the Kβ' line intensity to the total intensity of the Kβ line and the energy shift of the Kα1,2 lines was found by them. Fichter (1975) discussed the *Kα*-line shifts related to the oxidation number of the P-atom. The chemical shift of X-ray emission lines is usually interpreted with the effective charges or oxidation number of the X-ray emitting atom (Leonhardt&Meisel, 1970; Meisel et al., 1989). For example, the Al *Kα* lines shift to higher energy in going from the metal to the oxide (Nagel et al., 1974). By comparing the measured chemical shifts with those of the reference compounds, Gohshi et al. (1973, 1975) determined the chemical state of S, Cr and Sn. They obtained not only qualitative, but also quantitative results.

Theoretical studies of emission spectra were performed mostly to study atoms with simple electronic configurations (see, e.g., the review by Mukoyama et. al., 2004). Theoretical calculations for solids and molecules have been done mainly to predict transition energies and line profiles, but evaluation of transition probabilities is rather scarce. This is due to two reasons: Firstly, molecular orbital methods and band theories are originally developed for ground states and sometimes difficult to apply to excited states with an inner-shell vacancy. Secondly, matrix elements for absorption and emission processes in molecules include multi-center integrations, which are tedious and require long computing times. Most individual authors indicate that their results favor the Dirac-Hartree-Fock calculations of Scofield (1974a), rather than the significantly lower predictions of the same author's earlier Dirac-Hartree-Slater calculations (Scofield, 1969). Both of these describe the de-excitation of a single *K* vacancy in a neutral atom. However careful examinations (Salem et al., 1974; Khan&Karimi, 1980) of all available data reveal a tendency for *Kβ*/*Kα* to fall somewhat below the DHF predictions in the atomic number region 21<Z<32 where the 3*d* subshell is filling.

Band et al. (1985) applied the scattered-wave (SW) X*α* MO method to calculate the chemical effect on the *Kβ*/*Kα* intensity ratios. They performed the MO calculations for different chemical compounds of Mn and Cr using the cluster method and obtained the spherically averaged self-consistent potential and the total charge of the valance electrons in the central atom region. Chemical effect on the *Kβ*/*Kα* X-ray intensity ratios or some Mn and Cr compounds has been studied both theoretically and experimentally by Mukoyama et al. (1986). The *K* X-ray spectra were measured by the use of a double crystal spectrometer with high energy resolution. The theoretical calculations were made with the use of the discretevariational X*α* molecular-orbital method and the X-ray intensities were evaluated in the dipole approximation using molecular wave functions. Mukoyoma et al. (2000) have calculated the electronic structures of tetraoxo complexes of 4*d* and 5*d* elements with the discrete-variational *Xα* (DV-*Xα*) MO method. They found that the for Tc compounds, the calculated values were in good agreement with the measured values. In the case of Mo *K* Xrays, the agreement theory and experiment is not as good as with Tc compounds. Yamoto et

the rearrangement of electrons between 3*d* and 4*s* states of the metal or electron transfer

The chemical environment has a strong effect on the transitions originated in valence band and its influence could clearly be observed in the emission spectrum structure. The P-*Kβ* spectrum has been studied by many authors (Takashi, 1972; Taniguchi 1984; Torres Delluigi et al., 2003), who used both single-crystal and two-crystal spectrometers with conventional X-ray sources. These authors showed some modifications in the *Kβ* spectra and its relation with P chemical environment. Compounds with oxygen as ligand atom, a relationship between the ratio of the Kβ' line intensity to the total intensity of the Kβ line and the energy shift of the Kα1,2 lines was found by them. Fichter (1975) discussed the *Kα*-line shifts related to the oxidation number of the P-atom. The chemical shift of X-ray emission lines is usually interpreted with the effective charges or oxidation number of the X-ray emitting atom (Leonhardt&Meisel, 1970; Meisel et al., 1989). For example, the Al *Kα* lines shift to higher energy in going from the metal to the oxide (Nagel et al., 1974). By comparing the measured chemical shifts with those of the reference compounds, Gohshi et al. (1973, 1975) determined the chemical state of S, Cr and Sn. They obtained not only

Theoretical studies of emission spectra were performed mostly to study atoms with simple electronic configurations (see, e.g., the review by Mukoyama et. al., 2004). Theoretical calculations for solids and molecules have been done mainly to predict transition energies and line profiles, but evaluation of transition probabilities is rather scarce. This is due to two reasons: Firstly, molecular orbital methods and band theories are originally developed for ground states and sometimes difficult to apply to excited states with an inner-shell vacancy. Secondly, matrix elements for absorption and emission processes in molecules include multi-center integrations, which are tedious and require long computing times. Most individual authors indicate that their results favor the Dirac-Hartree-Fock calculations of Scofield (1974a), rather than the significantly lower predictions of the same author's earlier Dirac-Hartree-Slater calculations (Scofield, 1969). Both of these describe the de-excitation of a single *K* vacancy in a neutral atom. However careful examinations (Salem et al., 1974; Khan&Karimi, 1980) of all available data reveal a tendency for *Kβ*/*Kα* to fall somewhat below the DHF predictions in the atomic number region 21<Z<32 where the 3*d* subshell is

Band et al. (1985) applied the scattered-wave (SW) X*α* MO method to calculate the chemical effect on the *Kβ*/*Kα* intensity ratios. They performed the MO calculations for different chemical compounds of Mn and Cr using the cluster method and obtained the spherically averaged self-consistent potential and the total charge of the valance electrons in the central atom region. Chemical effect on the *Kβ*/*Kα* X-ray intensity ratios or some Mn and Cr compounds has been studied both theoretically and experimentally by Mukoyama et al. (1986). The *K* X-ray spectra were measured by the use of a double crystal spectrometer with high energy resolution. The theoretical calculations were made with the use of the discretevariational X*α* molecular-orbital method and the X-ray intensities were evaluated in the dipole approximation using molecular wave functions. Mukoyoma et al. (2000) have calculated the electronic structures of tetraoxo complexes of 4*d* and 5*d* elements with the discrete-variational *Xα* (DV-*Xα*) MO method. They found that the for Tc compounds, the calculated values were in good agreement with the measured values. In the case of Mo *K* Xrays, the agreement theory and experiment is not as good as with Tc compounds. Yamoto et

from the 3*d* state of the metal to the ligand atoms or vice-versa.

qualitative, but also quantitative results.

filling.

al. (1986) studied the variation of the relative *K* X-ray intensity ratios for compounds involving Tc isotopes, 95mTc, 97mTc and 99mTc. They found that the chemical effect on the *Kβ*/*Kα* ratios for 4*d* elements is small but the dependence of the *Kβ*2/*Kα* ratios on the chemical environments is appreciable.

Mukoyoma et al. (1986) have calculated the *Kβ*2/*Kα* intensity ratios for chemical compounds of 4*d* transition elements by the use of the simple theoretical method of Brunner et al. (1982), originally developed for 3*d* elements. Although they obtained good agreement between theories and experimental, it was found that their model is inadequate for the metallic cases.

These investigations on the effect of 3*d* and 4*d* electrons were performed only to understand the chemical effect on the X-ray intensity ratios. However, if the dependence on the excitation mode is also caused by the difference in the number of 3*d* electrons, as shown in our previous work, both effects, i.e. the dependence on the chemical environment and on the excitation mode, can be treated simultaneously to estimate the *Kβ*/*Kα* ratios in terms of the number of 3*d* electrons. However it may also be possible that these ratios are also expressed as a function of other parameters, such as bond length and effective number of 4*p* electrons. Considering these facts, it is interesting to study the dependence of the *Kβ*2/*Kα* ratio in 3*d* elements on various parameters of chemical compounds.

Iiahara et al. (1993) measured the *L* X-ray intensity ratios for some Nb and Mo compounds. When the measured *Lγ*1/*Lβ*1 ratios were plotted as a function of the effective number of 4*d* electrons, they found that the experimental data are experimental data are almost on a straight line. However, it should be noted that the 4*d*→2*p* transitions are allowed dipole transition and the 4d electron is the valance shell electron which participates directly in the X-ray emission. In this case the X-ray emission rate is proportional to the number of 4*d* electrons and increases with increasing effective number of 4*d* electrons.

The chemical behavior of actinide atoms (in particular, that of uranium) is determined by valance nl-electrons of three types: 7s, 6d and 5f. Although the bond energies of these electrons are almost equal, their wave-function differs greatly in distribution in the radial direction (Katz et al., 1986; Balasubramanian et al., 1994). It can be said that the 5f electrons have an only core arrangement in the atom. Therefore, when actinides chemical bonding is studied, several questions should be raised: (1) the possibility and form of 5f electrons participation in chemical bonding; (2) the necessity for taking into account the splitting of valance levels of the atom into two sublevels nl+ and nl- with total angular momentum j=1±1/2 because of the relativistic effect of spin-orbital splitting (SOS) (Pyykko,1988; Pepper et al., 1991); (3) the energetic stabilization of the specific chemical state of the heavy atom due to fine effects of electron density redistribution on valance orbital; (4) the possibility of independent participation of split subshells in chemical bond formation. One of the methods of modern precise spectroscopy capable of providing a correct description of chemical bonding process is the chemical shift (CS) method of X-ray emission lines, i.e. the change in their energy when the chemical state of the emitting atom is changed (Gohshi&Ohtsuka, 1973; Makarov, 1999; Batrakov et al., 2004).

Atomic theory has shown that the magnetic dipole moments observed in bulk matter arise from one or two origins: one is the motion of the electrons about their atomic nucleus (orbital angular momentum) and the other is the rotation of the electron about its own axis (spin angular momentum). The nucleus itself has a magnetic moment. Except in special types of experiments, this moment is so small that it can be neglected in the consideration of the usual macroscopic magnetic properties of bulk matter. When the atom is placed in an

Determination of Chemical State and External Magnetic Field

**2. Experimental** 

discussion below).

**2.1 Experimental set up (EDXRF)** 

Effect on the Energy Shifts and X-Ray Intensity Ratios of Yttrium and Its Compounds 95

to have been measured here for the first time. Secondly, spectra of *K* X-rays emitted from a Y target were measured in high resolution wave-length dispersive X-ray spectrometer (WDXRF). After the measurement, characteristic quantitative such as peak energy, indices of asymmetry, FWHM are determined. The measured spectra were described in terms of a background function (a straight line) and peaks having Gaussian profiles. The Microcal

Yttrium compounds can serve as host lattices for doping with different lanthanide cations and they used as a catalyst for ethylene polymerization. As a metal, it is used on the electrodes of some high-performance spark plugs. Yttrium is also used in the manufacturing of gas mantles for propane lanterns as a replacement for thorium, which is radioactive. Developing uses include yttrium-stabilized zirconia in particular as a solid electrolyte and as an oxygen sensor in automobile exhaust systems. Yttrium is used in the production of a large variety of synthetic garnets. Small amounts of yttrium (0.1 to 0.2%) have been used to reduce the grain sizes of chromium, molybdenum, titanium, and zirconium. It is also used to increase the strength of aluminium and magnesium alloys. The addition of yttrium to alloys generally improves workability, adds resistance to high-temperature recrystallization and significantly enhances resistance to high-temperature oxidation (see graphite nodule

The studied elements were Y, YBr3, YCl3, YF3, Y(NO3)3.6H2O, Y2O3, YPO4, Y(SO4)3.8H2O and Y2S3. The purity of commercially obtained materials was better than 99%. For powdered samples, particle size effects have a strong influence on the quantitative analysis of infinitely thick specimens. Even for specimens of intermediate thickness, in which category the specimens analyzed in the present study fall, these effects can be significant. Therefore, to circumvent particle size effects all samples were grounded and sieved through a -400 mesh (<37 μm) sieve. The powder was palletized to a uniform thickness of 0.05-0.15 g cm-2 range by a hydraulic press using 10 ton in-2 pressure. The diameter of the pellet was 13 mm. All of the lines were excited using a 100 mCi Am-241 annular radioactive source and Cd-109 point source of 10 mCi strength (providing 5.0x103 steradian-1 photon flux of Ag Xradiation). The fluorescent X-rays emitted from the targets were analyzed by a Si(Li)

detector (effective area 12.5 mm2, thickness 3 mm, Be window thickness 0.025 mm).

For each sample three separate measurements have been made just to see the consistency of the results obtained from different measurements agreed with a deviation of less than 1%. The experimental setup consist of a Si(Li) detector and Cd-109 radioactive source as shown in Fig. 1. The mechanical arrangement to house the source-sample-detector combination in a definite geometry was shown in Fig. 1. An Al, Pb conical collimator was used between the sample and the detector for the excitation to obtain a large beam of emergent radiation and to avoid the interaction of the X-rays emitted by the component elements of the radioactive capsule and detector.An Al, Pb conical collimator was used between the sample and the detector for the excitation to obtain a large beam of emergent radiation and to avoid the interaction of the X-rays emitted by the component elements of the radioactive capsule and detector. This collimator has an external diameter of 13 mm and it was placed in the internal diameter of the radioactive source (8 mm). A graded filter of Pb, Fe and Al to obtain a thin beam of photons scattered from the sample and to absorb undesirable radiation shielded the

Orgin 7.5 was used for peak resolving and background subtraction of *K* X-rays.

external magnetic field, the magnetic field produces a torque on the magnetic dipole. The torque is tending to align the dipole with the field, associated with this torque; there is a potential energy of orientation:

$$
\Delta E = \text{-} \mu\_l B \tag{1}
$$

*μl* is the orbital magnetic dipole moment of an electron. According to the quantum theory, all spectral lines arise from transitions of electrons between different allowed energy levels within the atom and the frequency of the spectral line is proportional to the energy difference between the initial and final levels. The slight difference in energy is associated with these different orientations in the magnetic field. In the presence of a magnetic field, the elementary magnetic dipoles, whether permanent or induced, will act to set up a field of induction of their own that will modify the original field.

Today investigations of magnetic effects on X-ray spectra became actual both from theoretical and experimental points of view. The numbers of works on this subject deal with magnetic circular dichroism (MCD) in X-ray absorption spectroscopy (XAS), that gives information on empty electron states in a valence band and their spin configurations (Thole et al., 1992, Stöhr&Wu, 1994). Several experiments have been performed on the external magnetic field effect on the *K* shell X-ray emission lines. Demir et al., (2006a) determined how the radiative transitions and the structures of the atoms in a strong magnetic field are affected, K*α* and K*β* X-ray production cross sections, the *K*-shell fluorescence yields and *I*(*Kβ/Kα*) intensity ratios for ferromagnetic Nd, Gd, and Dy and paramagnetic Eu and Ho were investigated using the 59.5 keV incident photon energy in the external magnetic fields intensities ± 0.75 T. On the other hand, Demir et al., (2006b) measured *L*3 subshell fluorescence yields and level widths for Gd, Dy, Hg and Pb at 59.5 keV incident photon energy in the external magnetic field of intensities ± 0.75 T. Porikli et al. (2008a; 2008b; 2008c) conduct measurements using pure Ni, Co, Cu and Zn and their compounds. Characteristic quantities such as position of line maxima, full widths at half maximum (FWHM), indices of asymmetry and intensity ratio values were determined in the values of external magnetic field 0.6 T and 1.2 T. Several experiments have been performed on the external magnetic field effect on the *K* shell X-ray emission lines. Commonly, experimental *L* X-ray intensities are measured using radioisotopes as excitation sources (Han et al., 2010; Porikli, 2011b). They have the advantages of stable intensity and energy and of small sizes, which allow compact and efficient geometry, and they operate without any external power.

Our motivation in performing this experiment has been two fold. First, with the aim of a better understanding of the chemical effect and external magnetic field effect, we conduct measurements using pure yttrium (Y) and its compounds. Characteristic quantities such as position of line maxima, full widths at half maximum (FWHM), indices of asymmetry and *Kβ*1/*Kα*, *Kβ*2/*Kα*, *Kβ*2/*Kβ*1 and *Kβ*/*Kα* intensity ratio values are determined in the values of external magnetic field 0.6 T and 1.2 T. In the present work, the measurements were done using a filtered 22.69 keV from Cd-109 and 59.54 keV from Am-241 point source and Si(Li) detector. Particle size effects were circumvented. Peak areas were determined using Gaussian fitting procedures and the errors in various corrections such as self-absorption and detector efficiency were minimized. The measured values were compared due to the external magnetic field and chemical effect. The measured values for B=0 were compared with other experimental and theoretical results. To our knowledge, these intensity ratio values of Y in the external magnetic field have not been reported in the literature and appear to have been measured here for the first time. Secondly, spectra of *K* X-rays emitted from a Y target were measured in high resolution wave-length dispersive X-ray spectrometer (WDXRF). After the measurement, characteristic quantitative such as peak energy, indices of asymmetry, FWHM are determined. The measured spectra were described in terms of a background function (a straight line) and peaks having Gaussian profiles. The Microcal Orgin 7.5 was used for peak resolving and background subtraction of *K* X-rays.
