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

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 $Ã$ 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 $Ã$ 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.