Observations of Population Inversion between theΛ-Doublet States of OH

Inverted population distribution between Λ-doublet states of OH produced in the reaction H + NO₂ {→} OH + NO has been observed in a beam maser and in a molecular-beam electric-resonance spectrometer. The observed inversions are of the order of 4-6% for the ²Π3/2, J=3/2, 5/2, 7/2, and the ²Π1/2, J=1/2 states, and less than 1% for the ²Π1/2, J=3/2, 5/2, 7/2, and 9/2 states.