Laser spectroscopy of the HgCd exciplex

Fluorescence and excitation spectra of HgCd were studied using pump-and-probe methods of laser spectroscopy with time resolution. A Hg-Cd vapor mixture, contained in a sealed quartz cell at 700 K, was irradiated by consecutive pump and probe dye-laser pulses. The pump radiation produced a population of Cd 5 ${}_{}{}^3{}_{}{}^{}$ ${\mathit{P}}_1$ atoms whose three-body collisions with Hg atoms resulted in the formation of HgCd excimers in the A$0^{\mathrm{-}}$, A$0^{+}$, and A1 states, correlated with the Cd 5 ${}_{}{}^3{}_{}{}^{}$P+Hg 6 ${}_{}{}^1{}_{}{}^{}$S manifold, which decayed, emitting a previously reported 4600-Å fluorescence continuum. The probe pulses, delayed by 450 ns, excited the excimers to the higher-lying C$0^{+}$ (Cd 5 ${}_{}{}^1{}_{}{}^{}$ ${\mathit{P}}_1$+Hg 6 ${}_{}{}^1{}_{}{}^{}$ ${\mathit{S}}_0$) state, which decayed to the repulsive X$0^{+}$ ground state, emitting fluorescence in the 2400–2650-Å region. We also observed a bound-bound excitation spectrum in the 5800–7100-Å region. A study of the time evolution of the excimer fluorescence yielded an approximate value for the three-body rate coefficient for HgCd formation, and an analysis of the spectra produced spectroscopic constants for the states involved in the transitions.