Formation and decay ofHg2excimers in Hg-Ar mixtures

The formation and decay of ${\mathrm{Hg}}_2$ molecules in their ${}_{}{}^3{}_{}{}^{}1_u^{}{}_{}{}^{}$ and ${}_{}{}^3{}_{}{}^{}0_u^{-}{}_{}{}^{}$ states, produced in Hg-Ar mixtures irradiated with 2537-Å Hg resonance radiation, has been investigated by the method of delayed coincidences. The mixtures which consisted of Hg vapor at a pressure of about 1 Torr and Ar at pressures of 45-720 Torr and which were contained in a quartz fluorescence cell, were excited with pulses of light, and the decay spectra of the 3350- and 4850-Å molecular fluorescent bands were studied in relation to Ar pressure. Analysis of the decays indicates that the effective cross sections for ${}_{}{}^3{}_{}{}^{}1_u^{}{}_{}{}^{}\leftrightarrow {}_{}{}^3{}_{}{}^{}0_u^{-}{}_{}{}^{}$ mixing, induced in ${\mathrm{Hg}}_2$-Ar collisions are of the same order as the ${\mathrm{Hg}}_2$-${\mathrm{N}}_2$ mixing cross sections, leading to the conclusion that the 4850-Å band is emitted mainly by ${}_{}{}^3{}_{}{}^{}0_u^{-}{}_{}{}^{}$ molecules in high vibrational states.