High resolution study of the six lowest doubly excited vibrational states of PH2D

The five lowest doubly excited deformational vibrational bands ν4 + ν6, 2ν6, ν3 + ν4, ν3 + ν6, and 2ν3 of PH2D have been recorded for the first time using a Bruker 120 HR interferometer with a resolution 0.0033 cm−1 and analysed. Some transitions belonging to a very weak band 2ν4 have been also assigned. From the fit 24 and 86, respectively, diagonal and resonance interaction parameters were obtained which reproduce 1089 upper energy levels obtained from more than 4600 assigned transitions with the rms deviation of 0.00059 cm−1.