**A. Appendix A**

The drift velocity of positive ion neon gas is: *w*<sup>þ</sup> ¼ ð Þ 11*:*27*E=n =* ð Þ 1 þ 0*:*01288*E=n* <sup>0</sup>*:*<sup>5</sup> (m/s) [52] where E/N is in Td. The metastable lifetime of neon gas is equal to 14*:*73 s [53]. The diffusion coefficient of metastable atoms is *Dm* <sup>¼</sup> 150 cm<sup>2</sup> <sup>s</sup> �<sup>1</sup> Torr [54]. The energy loss of an excited atom is 16.6 eV. The Ionization energy of neon gas is equal to 21*:*56454 eV. The energy loss (Pec) per electron due to elastic collision of electrons with the background gas is calculated according to [31, 55]. The rate coefficient of chemo-ionization processes is *Kci* <sup>¼</sup> <sup>3</sup>*:*<sup>6</sup> � <sup>10</sup>�<sup>10</sup> cm<sup>3</sup> <sup>s</sup> �<sup>1</sup> for T = 310 K [56]
