Laser spectroscopy of supersonic expansions of ICL

Abstract

High-resolution fluorescence excitation spectra of the B³Π(0⁺)–X¹Σ⁺ system of ICl, rotationally cooled in a seeded supersonic expansion, have been obtained using a single-mode c.w. dye laser. Problems due to overlap with ICl(A–X) and contaminant I₂(B–X) bands, are significantly reduced by the extreme cooling and a number of previously unreported ICl(B–X) bands, including the 0–0 fundamental, have been observed. The analysed spectra give improved molecular constants for the B states of both I³⁵ Cl and I³⁷ Cl, and the X state of I³⁷ Cl. Rotational and vibrational temperatures of the ICl in various carrier gases are given and discussed. No fluorescence signals attributable to ICl–rare-gas van der Waals complexes were observed; possible reasons for this are also discussed.