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

We report a detailed high resolution rovibrational analysis of the nu (1) fundamental absorption band system of CF3I, which appears as a very complex resonance polyad. Pulsed slit jet diode laser spectra (instrumental bandwidth less than or equal to 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 nu (1)(nu (0)=1076.0551 cm(-1)), 2 nu (0)(5)(nu (0)=1079.6732 cm(-1)) and nu (3)+3 nu (+/-3)(6)(nu (0)=1072.3884 cm(-1)), and the local Coriolis perturber nu (3)+3 nu (+1)(6)(nu (0)=1074.1845 cm(-1)). The level nu (3)+3 nu (+3)(6) was observed and included for the first time, and an additional anharmonic coupling between the levels nu (3)+3 nu (+3)(6) and nu (3)+3 nu (-3)(6) proved relevant. In order to analyze the higher J, K regions, perturbations arising from 2 nu (+/-2)(5) 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 2 nu (+/-2)(5). The results are discussed in relation to infrared multiphoton excitation of CF3I, infrared absorption in the atmospheric window and intramolecular vibrational redistribution. (C) 2002 American Institute of Physics.