Quenching of 6s6d and 6s7d Hg atoms by Hg*-Hg,Hg*-Ar and Hg*-N2 collisions

The radiative decays and collisional quenching of Hg 6¹D₂, 6³D₂, 7¹D₂ and 7³D₂ atoms were investigated by time-resolved methods. Hg vapour, pure or mixed with a buffer gas in a fluorescence cell, was irradiated with u.v. light pulses from a frequency-doubled N₂ laser-pumped dye laser, populating selectively each state in turn by 2-photon absorption from the 6¹S₀ ground state. Fluorescent components arising from the decays to the 6¹P₁ or 6³S₀ state were resolved with a spectrometer and their time evolutions recorded with a transient digitizer or time-to-amplitude converter and pulse-height analyzer, yielding the respective decay rates. The quenching cross sections were obtained from variations of measured decay rates with Hg or buffer-gas density.