The infrared spectrum of PF$_3$ and analysis of rotational energy clustering effect

In this paper we carry out the first variational calculation of the rotational-vibrational levels of PF$_3$ and computeintensities for dipole transitions between them. This is accomplished using new state of the art potential energy and dipolemoment surfaces (PES and DMS respectively). This allows the infrared spectrum of PF$_3$ to be simulated, providing a completeoverview of the spectrum. We also investigate theoretically the behaviour of PF$_3$ at high rotational excitations. The formation of quasi-degenerate 6-fold rotational energy clusters at high rotational excitation are investigated, up to $J$=270, which are found to occur around $J$=200. The wavefunctions are analysed in terms of semi-classical rotational energy surfaces