The 1,3B 1— 1A 1 systems of the nitrite anion in a NaHCO 2 host crystal

The lower energy electronic transitions of the NO ^?₂ anion in a NaHCO ₂ host crystal at 4 K are reported and analyzea. The ¹B ₁— ¹A ₁ system, whose origin is at 25 649 cm ^?1, is seen in absorption and fluorescence accompanied by a long progression in the symmetric bending mode (ν′ ₂ = 626, ν″ = 820 cm ^?1). The implied change in the ONO bond angle is 9 ± 3 ⁰. The ³B ₁ → ¹A ₁ phosphorescence is quite weak with an extrapolated origin at 18 059 cm ^?1. The ¹B ₁ ← ¹A ₁ absorption linewidths, the lower-resolution fluorescence photoexcitation spectrum, and the relative phosphorescence and fluorescence intensities suggest the involvement of an intermediate state in populating the triplet manifold after excitation of the ¹B ₁ state.