Measurement of Hönl–London factors on 2Σ+–2Π transitions in NO

Hönl–London factors for 2Σ–2Π transitions in the NO molecule have been measured for the first time, using single photon vacuum UV excitation of the A 2Σ+ and of the D 2Σ+ state. The measured and the calculated line intensities in the subsequent fluorescence are found to be in very good agreement for all 12 branches. The J dependence of the relative line intensities clearly reveals the transition from Hund’s coupling case (a) to case (b) for the 2Π ground state.