High resolution analysis of the complex symmetric CF3 stretching chromophore absorption in CF3I

We report a detailed high resolution rovibrational analysis of the n 1 fundamental absorption band system of CF3I, which appears as a very complex resonance polyad. Pulsed slit jet diode laser spectra ~instrumental bandwidth <25 MHz! of CF3I ~neat and seeded in He! at rotational temperatures of about 7, 30, and 70 K have been obtained. The low J, K part of the observed transitions can be fitted by a model including the anharmonically coupled levels n 1(n~ 0 51076.0551 cm21), 2n5 0 (n~ 051079.6732 cm21) and n 313n 6 63(n~ 051072.3884 cm21), and the local Coriolis perturber n 313n 6 11(n~ 051074.1845 cm21). The level n 313n 6 13 was observed and included for the first time, and an additional anharmonic coupling between the levels n 313n 6 13 and n 313n 6 23 proved relevant. In order to analyze the higher J, K regions, perturbations arising from 2n 5 62 turned out to be important. In certain regions of the spectra, effects due to nuclear quadrupole interaction are clearly visible. We report new sets of parameters for a low J, K model and for an extended model including the perturber 2n 5 62. The results are discussed in relation to infrared multiphoton excitation of CF3I, infrared absorption in the atmospheric window and intramolecular vibrational redistribution.