Optogalvanic spectrum of Ar excimers in a dc discharge with supersonic expansion

Optogalvanic spectra have been obtained arising from transitions between electronically excited states of excimers formed in a dc discharge with supersonic expansion. In this method, tunable cw laser radiation is incident on the discharge while optogalvanic signals are measured directly across the discharge electrodes. The primary advantage of the method is its high sensitivity, as known in atomic spectroscopy. As an example, an optogalvanic spectrum of the 3Πg←3Σu+ transition of Ar2∗ near 990 nm is shown.