High-Resolution Infrared Study of PHD 2: The P–H Stretching Bands ν 1 and 2ν 1

For the first time the infrared spectrum of PHD 2 was recorded in the region of the PH stretching fundamental ν 1 at 2324.005 cm −1 and the overtone 2ν 1 at 4563.634 cm −1 with a resolution of 4.2×10 −3 cm −1 and 8.8×10 −3 cm −1, respectively. In the analyses about 1340 and 1020 transitions were assigned to the corresponding ν 1 and 2ν 1 bands, which provided 316 and 248 upper energies, respectively. Since both the bands are sufficiently isolated, a standard Watson-type Hamiltonian ( A-reduction, I r -representation) was employed. The obtained sets of spectroscopic parameters correlate very well both with each other, and with the corresponding parameters of the ground vibrational state.