Optogalvanic spectroscopy of quasi-resonant Penning ionization

Quasi-resonant Penning ionization in a Ne-Ca discharge is detected and studied by using the pulsed optogalvanic effect on the neon 1s _i→2p_j transitions. The ensuing signals exhibit extra features which appear at longer times following the signals obtained in pure neon discharge. A phenomenological model is used to describe the signal and to extract an estimate of the Penning cross section, which is on the order of 10^-14 cm². At high discharge currents the Penning contribution becomes unimportant and the related features in the optogalvanic signal disappear. A correlation between the dependence of the emission intensity of certain transitions of Ca and Ca⁺ related to the Penning effect and the dependence of the optogalvanic signal due to the Penning ionization on the discharge current is demonstrated. A similar correlation between the I-V characteristics and the dependence of the optogalvanic signal on the discharge current is also shown.