Abstract

This paper presents the first measurements of the absolute photoabsorption spectrum of Kr₂F(4²Γ) from 248 to 600 nm. Absolute cross sections were measured at thirty-seven wavelengths using a fluorescence suppression technique. An extension of this approach was developed to measure relative absorption cross sections over a given spectral range as a dye laser was continuously scanned. Absorption scans were made for 337 ≤ λ ≤ 600 nm and were scaled to the absolute cross sections within each spectral region. The excited Kr₂F molecules were formed by laser irradiation of Kr/F₂ mixtures (typically 1000-Torr Kr:1-Torr F₂) at 193 or 248 nm. In each case, photoabsorptive losses induced by a delayed probe beam resulted in an obvious suppression of the Kr₂F(4²Γ) spontaneous emission. The resulting absorption spectrum displays a distinct absorption maximum (σ = 1.0 × 10⁻¹⁷ cm²)at ~337 nm. The red wing of the absorption profile displays several reproducible secondary maxima (at 397, 426, and 471 nm) as the cross section falls to < 5 × 10⁻¹⁹cm² at 600nm. Two of the three undulations have not been predicted theoretically. On the blueside of the peak, the cross section drops to ~1.5 × 10⁻¹⁸ cm² at 248 nm. Although the peak absorption is located near the predicted wavelength, the 4²Γ → 9²Γ absorption cross section is weaker than the associated ${\text{Kr}}_2^{+}1{\left(1/2\right)}_{\text{u}}\to 2{\left(1/2\right)}_{\text{g}}$ transition by a factor of ~3. Preliminary measurements of the ${\text{Kr}}_2^{+}$ absorption cross section and the implications of these results for the Kr₂F laser are also discussed.

© 1986 Optical Society of America