Continuum absorption spectra in the far wings of the Hg 1S0-->3P1 resonance line broadened by Ar.

Abstract

Absolute reduced absorption coefficients for the Hg resonance line at 253.7 nm broadened by Ar were determined between 390 and 430 K in the spectral range from 20 to 1000 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ on the red wing and from 20 to 400 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ on the blue wing. The resultant reduced absorption coefficients are in fair agreement with those obtained by Petzold and Behmenburg [Z. Naturtorsch. Teil A 33, 1461 (1978)]. The observed A${\mathrm{}}^{3}$${0}^{+}$\ensuremath{\leftarrow}X${\mathrm{}}^{1}$${0}^{+}$ spectrum in the spectral range from 80 to 800 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ on the red wing agrees remarkably well both in shape and magnitude with the quasistatic line shape calculated using the potential-energy curves of the HgAr van der Waals molecule given by Fuke, Saito, and Kaya [J. Chem. Phys. 81, 2591 (1984)], and Yamanouchi et al. [J. Chem. Phys. 88, 205 (1988)]. The blue-wing spectrum is interpreted as the B${\mathrm{}}^{3}$1\ensuremath{\leftarrow}X${\mathrm{}}^{1}$${0}^{+}$ free-free transition of HgAr by a simulation of the spectrum using uniform semiclassical treatment for the free-free Franck-Condon factor. The source of the satellites on the blue wing is attributed to the phase-interference effect arising from a stationary phase-shift difference between the B- and X-state translational wave functions. The stationary phase-shift difference arises owing to the existence of a maximum in the difference potential between the B and X states. The repulsive branches of the potential-energy curves of HgAr for the X and B states have been revised to give excellent agreement between the observed and calculated spectra, both in shape and magnitude. \textcopyright{} 1996 The American Physical Society.