Absorption and fluorescence of OClO Ã 2A2–X̃ 2B1 in solid Ne, Ar, and Kr. I. Vibrationally unrelaxed Ã→X̃ emission

Abstract

Dispersed laser-induced fluorescence of the à 2A2→X̃ 2B1 transition of OClO in solid Ne in the spectral range 500–770 nm was recorded when the origin at 20 991 cm−1 was excited. Progressions with spacings near 939 and 446 cm−1 are associated with vibrational modes ν1 and ν2 of the X̃ state. A simultaneous fit of both modes yields ω1″=957.1±1.4, ω2″=452.6±0.4, x11″=4.47±0.04, x22″=0.54±0.05, and x12″=4.00±0.05 cm−1. When the 101 line of the ÖX̃ system at 21 699 cm−1 was excited, vibrationally unrelaxed emission was observed in the spectral region 480–600 nm. Excitation of the 201 line at 21 284 cm−1 generated weak vibrationally unrelaxed progressions. The visible absorption spectrum of OClO in solid Ne in the region 415–488 nm was recorded with a Fourier-transform spectrometer, yielding ν00=20 991.3, ν1′=707.9, ν2′=292.5, and 2ν3′=887.6 cm−1 for the à state. Simultaneous fits considering either only ν1 and ν2 modes or all three modes yield corresponding spectral parameters. Similar experiments were performed with OClO in solid Ar and Kr. Pronounced increases in ν1′ (716.0 cm−1 in Ar and 712.5 cm−1 in Kr) and ν2′ (302.3 cm−1 in Ar and 303.0 cm−1 in Kr) and a decrease in ν00 (188 cm−1 and 331 cm−1 red-shifted, respectively) from that in the gas phase indicate substantial perturbation of the à state in solid Ar and Kr. An absorption continuum underlying the ÖX̃ system is attributed to absorption to the 1̃ 2A1 state above the predissociation barrier. The phonon interaction increases and the threshold of the continuum decreases as the matrix host is altered from Ne to Ar to Kr.