Emission spectra of Cs-He excimers in cold helium gas

We observed broadband emission spectra of Cs-He excimers $\left({\mathrm{Cs}}^{*}\mathrm{He}\right)$ in cold He gas $(1.3\mathrm{}–100\mathrm{K}),$ when Cs atoms were excited to the $6{}^{2}P$ states. We calculated the emission spectrum from each vibrational state of ${\mathrm{Cs}}^{*}\mathrm{He}$ using Pascale’s semiempirical Cs-He potential energy curves [J. Pascale, Phys. Rev. A $28,$ 632 (1983)], and compared the results with the observed spectra. From the measured spectral shape, we estimated the relative populations of the vibrational states of ${\mathrm{Cs}}^{*}\mathrm{He}$ at various He gas densities, and estimated the predissociation rate of ${\mathrm{Cs}}^{*}\mathrm{He}$ in the $A{}^2{\Pi }_{1/2}$ state. Moreover, a broadband emission spectrum of ${\mathrm{Cs}}^{*}{\mathrm{He}}_2$ was also observed, which was compared with that observed in liquid He.