Abstract

The time dependence of the optogalvanic signals induced by 1sj→2pk (Paschen notation) pulsed laser excitations of neon in a low power ∼30 MHz radio frequency (rf) discharge at ∼5 Torr has been investigated. The method of Kumar and McGlynn [Chem. Phys. Lett. 176, 536 (1991)] has been improved and is used to separate the temporal profiles of the optogalvanic signals into two components: one attributable to ionization rate changes and the other to acoustic effects. This separation simplifies the identification of the kinetic processes which produce optogalvanic signals. Selective laser excitation of 2pk states, ones which possess quite different decay branching ratios to the metastable and nonmetastable 1sj states, reveals time dependencies due to unique perturbations of specific 1sj populations. No dimer mediated nor, indeed, any effects associable with 2pk state populations contribute to the profiles. Competitive processes which increase or decrease the ionization rates are identified at t≥1 μs. The extensive broadening of the acoustic and ionization components is caused by radiation trapping of 1s2→1S0 and 1s4→1S0 photons.

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