Need help understanding E/p V/cm.torr
Courtesy of Wiki https://en.wikipedia.org/wiki/Torr

N2 608 torr * 0.06cm gap = 36.5 torr-cm
@ 7500V it seems to be 3x the breakdown voltage, Vb.
I cannot explain what is optimal but at 0.6mm gap, it will trigger an arc, I guess sustained by lasing and current limiting.