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.