Selective population of N = 3 OVIII level during expansion of laser plasma in helium

The mechanism underlying the formation of inverse population of levels of multiply charged ions on the basis of recharging is realized experimentally for the first time. The experimental setup consisted of a neodymium glass laser, a vacuum chamber and a X-ray spectrograph. The experiments were conducted with spatial resolution along the plasma flame, using a pulse length of approximately 0.5 ns. It is found experimentally that when a laser plasma flame containing multiply charged oxygen ions expands, the OVIII oxygen levels become selectively populated due to recharging of the oxygen nuclei on helium ions.