Absorption and fluorescence of OClO Ã ² A ₂ -X̃ ² B ₁ in solid Ne, Ar, and Kr. I. Vibrationally unrelaxed Ã→X̃ emission

Dispersed laser-induced fluorescence of the à ² A ₂ →X̃ ² B ₁ transition of OClO in solid Ne in the spectral range 500-770 nm was recorded when the origin at 20991cm ^-1 was excited. Progressions with spacings near 939 and 446cm ^-1 are associated with vibrational modes ν ₁ and ν ₂ of the X̃ state. A simultaneous fit of both modes yields ω ₁ ^″ =957.1±1.4, ω ₂ ^″ =452.6±0.4, x ₁₁ ^″ =4.47±0.04, x ₂₂ ^″ =0.54±0.05, and x ₁₂ ^″ =4.00±0.05cm ^-1 . When the 1 ₀ ¹ line of the Ã-X̃ system at 21699cm ^-1 was excited, vibrationally unrelaxed emission was observed in the spectral region 480-600 nm. Excitation of the 2 ₀ ¹ line at 21284cm ^-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 ν ₀₀ =20991.3, ν ₁ ^′ =707.9, ν ₂ ^′ =292.5, and 2ν ₃ ^′ =887.6cm ^-1 for the à state. Simultaneous fits considering either only ν ₁ and ν ₂ modes or all three modes yield corresponding spectral parameters. Similar experiments were performed with OClO in solid Ar and Kr. Pronounced increases in ν ₁ ^′ (716.0cm ^-1 in Ar and 712.5cm ^-1 in Kr) and ν ₂ ^′ (302.3cm ^-1 in Ar and 303.0cm ^-1 in Kr) and a decrease in ν ₀₀ (188cm ^-1 and 331cm ^-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 Ã-X̃ system is attributed to absorption to the 1̃ ² A ₁ 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.