Rovibrational study of the CH2 wagging fundamental of monofluoroacetonitrile

The vapor-phase infrared spectrum of monofluoroacetonitrile (CH2FCN) has be en recorded at high resolution in the v(4) band region (1363-1398 cm(-1)) u sing a tunable diode laser spectrometer. A detailed assignment of the rotat ional structure of the expected a-/b-hybrid band has been made for a-type t ransitions with Ka less than or equal to 19, J less than or equal to 61. Th e b-type transitions were too weak to be observed. Upper state spectroscopi c constants including the sextic terms have been obtained from a set of unp erturbed data employing the Watson A-reduced Hamiltonian in the I' represen tation. A number of perturbed transitions have been accounted for, includin g b- and c-type Coriolis resonances and anharmonic resonances between v(4) and the nearby levels v(5) + v(12) and v(11) + v(12). The vibrational energ ies of these perturbing levels have been obtained from the reanalysis of th e low-resolution infrared spectrum. Rotational constants and the band origi n of the perturbers along with the interaction parameters with the v(4) = 1 state have also been determined. (C) 2001 Academic Press.