A 3B1–1A1 electronic transition of the NO –2 ion

Abstract

A new absorption system of NO^–₂ in the visible and near ultra-violet has been found in large single crystals of sodium nitrite. Sharp vibrational and librational structure is observed at 20°K, giving v₀₀= 18959 cm^–1, ω′₁= 1112 cm^–1 and ω′₂= 644 cm^–1. Polarization measurements and studies of the Zeeman effect with a pulsed magnet show that the electronic transition is ³B₁–¹A₁. The transition arises from the one-electron promotion (2b₁)â†�(4a₁), and the ONO angle is estimated to increase from 116° in the ¹A₁ ground state to 130° in the ³B₁ state. The principal source of the intensity of this singlet-triplet transition is intensity stealing from the ¹B₂–¹A₁ transition at 2100 Å.