Photoattenuation in the extreme red wings of Xe and Kr resonant lines

Photoattenuation coefficients are reported for high-pressure xenon and krypton at wavelengths in the red wings of the first resonant lines [$\mathrm{Xe}\left({}_{}{}^3{}_{}{}^{}P_1^{}{}_{}{}^{}\right)$, ${\lambda }_0=1470\mathrm{}$ Å and $\mathrm{Kr}\left({}_{}{}^3{}_{}{}^{}P_1^{}{}_{}{}^{}\right)$, ${\lambda }_0=1236\mathrm{}$ Å]. The measurements cover the range 2000-20 000 ${\mathrm{cm}}^{-1\mathrm{}}$ from the resonant lines. The photoattenuation spectra are interpreted in terms of Rayleigh scattering and photoabsorption by atoms, Van der Waals molecules, and unbound diatomic molecules—different portions of the spectra are dominated by different species and phenomena. Absorption by unbound diatomic molecules is interpreted via a quasistatic model of the molecule. Analysis of the data in this manner yields information concerning the structure and radiative lifetime of the lowest-bound diatomic states of $\mathrm{Xe}_2^{}{}_{}{}^{*}$ and $\mathrm{Kr}_2^{}{}_{}{}^{*}$. The significance of the results reported here in regards to dissociative noble-gas lasers (transition from a bound diatomic level to the repulsive ground level) is discussed.