The v2 and v4 bending fundamental bands of PD3

Infrared spectra of PD3 have been recorded in the 600-1160 cm-1 range at a resolution of 0.0023 cm-1. About 2500 rovibrational transitions have been measured and assigned to the v2(A1) and v4(E) bending fundamentals, including 131 "perturbation allowed" transitions with selection rules Δ(k-1) = ±3 and ±6. Splittings of the K″ = 3, 6, and 9 lines were observed. The rotational structure in the v2 = 1 and v4 = 1 vibrational states up to J = K = 28 was reproduced by fitting simultaneously all experimental data. The adopted rovibrational Hamiltonian explicitly takes into account the Coriolis and k-type interactions between the v2 = 1 and v4 = 1 states, and includes also several essential resonances within these states. Two different reductions of the Hamiltonian were adopted in the fitting procedure. The 41 parameters in model 1 reproduced 2435 IR transitions retained in the final cycle with a standard deviation of the fit equal to 2.06 × 10-4 cm-1 (about the precision of experimental measurements); in model 2, 45 parameters reproduced 2428 transitions with the same value of standard deviation. The equivalence of the two sets of parameters has been demonstrated.