Emission Spectrum of NO in Solid Rare Gases: The Lifetime of the a 4Π State and the Spectrum of the a 4Π→X 2Π and B 2Π→X 2Π Transitions

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Abstract
The emission spectrum of NO molecules trapped in solid argon and krypton has been excited with x rays. Two series of bands have been observed, the well‐known β bands (B 2Π→X 2Π) and a series with estimated origin near 38 000 cm—1 believed to be the a 4 Π 5 2 →X 2 Π 3 2 transition. The lifetime of the assumed quartet state has been measured in solid Ne, Ar, and Kr and found to be 156, 93, and 35 msec, respectively, in these solids. These lifetimes are compatible with the above assignment of the bands. A least‐squares fit has been made of the spectral data to obtain the 0–0 band positions and the vibrational constants of the NO molecule in the solid. The doublet—quartet bands are believed to arise from a spin—orbit mixing of the a 4 Π 5 2 state with the B′ 2 Δ 5 2 state. The possibility of observing high resolution spectra of the a 4Π—X 2Π transition in either absorption or emission is considered. The role of the a 4Π state of NO in photochemical reactions and in auroral and airglowspectra is briefly discussed.