Absorption coefficients for the wing of the Sr resonance line at 4607 AA broadened by Ar and Xe

Abstract

Absolute absorption coefficients for the Se resonance line at 4607 AA perturbed by Ar and Xe below one atmosphere were measured in the spectral range from 1 to 100 cm-1 on either side of the line centre. The coefficients are proportional to the product of the Sr and rare-gas densities, as expected from line broadening produced by binary collisions between Sr and rare-gas atoms. Using the unified Franck-Condon (UFC) approximation of Szudy and Baylis (1975), the difference interaction potential Delta V(r) was determined. A UFC profile for a van der Waals potential with coefficient Delta C6=2.0*10-58 (8.9*10-58) erg cm6 for Sr-Ar (Sr-Xe) gives a good fit for the red wing near the line centre but shows a systematic discrepancy for the blue wing. The shoulder in the red wing is explained by a minimum of Delta V(r) with a well depth of E=20(50) cm-1 at the interatomic distance r=5.9(6.7) AA for Sr-Ar (Sr-Xe). The results are compared with previous measurements.