Theoretical background and preliminary results of the global modeling of the lower three polyads of PH3 covering the 3 to 10 µm spectral region

A recent study reported in 2006 provided an empirical database of PH3 (line positions and intensities) in the 3 μm region. The study was based experimentally on FTIR spectra recorded at Kitt Peak at various optical densities and theoretically on single state fits of features assigned using the ground state combination differences method. The need for a complete analysis of the octad was underlined in order to account for the complex interactions which is expecially important for intensity modeling. The polyad pattern of the PH3 molecule presents close similarities with those of spherical top molecules (like CH4), although the symmetry degeneracies are reduced. The simultaneous analysis of t…