Knowledge Bank

In order to account for the $PH3$ features observed in the Jovian spectrum at $5\mu m$, the three interacting bands $2\nu 2,\nu 2+\nu 4$ and $2\nu 4$ contributing to the absorption in the window $2050-2150cm-1$ were analyzed from laboratory $spectra\ast$. The parallel and perpendicular components of the $2\nu 4$ (strongly overlapped at room temperature by the red wings of $\nu 1$ and $\nu 3$) where assigned for the first time, from a low temperature spectrum. The three bands were analyzed within a triad Hamiltonian model where the strong Coriolis couplings among the upper vibrational states were explicitly included in the energy metrix before diagonalization. The series of required computing programs was similar to that previously set up for the analysis of $CH3D$ at $6-10\mu m(1)$. The energy and intensity parameters presently derived were used for modelling the absorption frequencies and intensities in the window. All transitions predicted with line strengths above the lower limit of $4.10-25$ cm/molecule were taken into account.