The effects of multi-mode CW laser-induced perturbations of neon metastable states on optogalvanic phenomena in pre-breakdown discharges

Abstract

Optogalvanic effects have been induced in the pre-breakdown regime in neon by the use of a CW ring dye laser operating in the wavelength range 550-650 nm. Those effects that arise when the dye laser output is allowed to operate in the multi-mode configuration at a wavelength tuned to a particular neon transition from one of the four 1s to one of the ten 2p energy levels have been investigated. The strong influence of the energetic metastable 1s5 particle has been examined in detail by inducing its transition to the 2p4 level with laser radiation tuned to 594.5 nm. The effect of collisional coupling between the closely spaced 1s levels complicates the interpretation of the observed temporal and spatial changes in the nanoampere pre-breakdown ionization currents following the laser-induced perturbation. The relevant coupled differential equations, relating the particle densities appropriate to the levels of the 1s manifold and the 2p4 state, have been solved. These solutions, in conjunction with an extension of the Molnar treatment for the temporal growth of ionization in the presence of two or more metastable particles, have led to determinations of the diffusion coefficients, the fundamental time constants associated with the diffusion processes, the corresponding quenching parameters linked to the effects of trace impurities, as well as the specific action of the laser radiation. Observations of the variation of the fundamental time constant with laser intensity agree well with theoretical predictions but lead to some unexpected consequences concerning the identity of the unperturbed residue.

Homogeneous gas phase models of relaxation kinetics in neon afterglow

“…However, it should be mentioned that depopulation of Ne( 3 P 2 ) by 588.2nm line were studied shorter than 3ms in the afterglow [5]. In another paper [6], depopulation of Ne( 3 P 2 ) was examined by laser irradiation tuned to 594.5nm shorter than 7ms in the afterglow in accordance with our analysis. Namely, this metastable state is quenched very efficiently by numerous collisions with ground state atoms, electrons, walls and between themselves and even elementary considerations show that its effective lifetime is very short on the time scale of the observations of memory effect.…”