Vibrational anharmonicity constants for SF6. I. A 16 μ diode laser study of transitions in the ν4 region

A total of eight empirical anharmonicity constants have been determined from diode laser studies of the ν4 vibrational transitions in SF6. The transitions from the low excited states on the 16 μ region were recorded using semiconductor lasers with a long optical path absorption cell. The relative intensities of the corresponding Q branches were related to the population distribution in the temperature range from 160 to 300 K in order to make the spectroscopic assignments of the ν4 hot band transitions. These measured states represent some 86% of the total population distribution of the SF6 molecules at 300 K. Theoretical models based on Morse potential functions are discussed and the results from the model calculations are compared with the experimental vibrational anharmonicity constants