Effect ofHg2-Hg collisions on the formation and decay of excitedHg2molecules in Hg-N2mixtures

Abstract

The effect of ${\mathrm{Hg}}_{2}$-Hg collisions on the formation and decay of excited ${\mathrm{Hg}}_{2}(^{3}1_{u})$ and ${\mathrm{Hg}}_{2}(^{3}0_{u}^{\ensuremath{-}})$ molecules in Hg-${\mathrm{N}}_{2}$ mixtures was investigated in a series of delayed-coincidence experiments. $\mathrm{Hg}(^{3}P_{1})$ atoms, formed by irradiating the vapor-gas mixture with pulses of Hg (2537 \AA{}) resonance radiation, were transferred collisionally to the $^{3}P_{0}$ state. The ${\mathrm{Hg}}_{2}(^{3}1_{u})$ molecules, formed in subsequent $\mathrm{Hg}(^{1}S_{0})+\mathrm{Hg}(^{3}P_{0})+{\mathrm{N}}_{2}$ collisions, underwent collisional $^{3}1_{u}\ensuremath{\rightarrow}^{3}0_{u}^{\ensuremath{-}}$ mixing. The time-decay spectra of the 3350 and 4850-\AA{} fluorescent bands, associated with the $^{3}1_{u}$ and $^{3}0_{u}^{\ensuremath{-}}$ states, respectively, were studied in relation to ${\mathrm{N}}_{2}$ and Hg densities and the resulting decay constants were extrapolated to zero ${\mathrm{N}}_{2}$ and Hg pressures, yielding the following total cross sections $Q(A\ensuremath{\rightarrow}B)$ for collisional transfer between states $A$ and $B$. For ${\mathrm{Hg}}_{2}$-${\mathrm{N}}_{2}$ collisions: $Q(^{3}0_{u}^{\ensuremath{-}}\ensuremath{\rightarrow}^{3}1_{u})=2.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}21}$ ${\mathrm{cm}}^{2}$; $Q(^{3}0_{u}^{\ensuremath{-}}\ensuremath{\leftarrow}^{3}1_{u})=6.9\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}17}$ ${\mathrm{cm}}^{2}$; for ${\mathrm{Hg}}_{2}$-Hg collisions: $Q(^{3}0_{u}^{\ensuremath{-}}\ensuremath{\rightarrow}^{3}1_{u})=2.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}17}$ ${\mathrm{cm}}^{2}$; $Q(^{3}0_{u}^{\ensuremath{-}}\ensuremath{\leftarrow}^{3}1_{u})=6.8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}14}$ ${\mathrm{cm}}^{2}$. The radiative lifetime ${\ensuremath{\tau}}_{4}^{0}$ of the $^{3}0_{u}^{\ensuremath{-}}$ state was found to be 21.4 msec \ifmmode\pm\else\textpm\fi{} 7%.