High resolution reinvestigation of the ν14 band of pyrrole near 722 cm −1

Relying on three high resolution (0.0015cm−1) Fourier transform spectra, the positions of 5285 lines of the ν14 band of pyrrole were measured in the range 684–758 cm−1 with absolute uncertainties from 5.1×10−5 to 1.1×10−4cm−1. P and R line positions in the ν14 band together with those of the ν16 and 2ν16 bands from the literature were used to generate 4603 ground state combination differences. A weighted least squares fit of this data with 167 pure rotation transitions from the literature allowed determining the sextic centrifugal distortion constant HJ for the first time. Rotational and centrifugal distortion constants were obtained for the v14=1 level. Together, both sets of constants provide a precise modelling of the positions and relative intensities of the ν14 band lines. This investigation was motivated by the resolution of the recorded spectra, more than 5 times higher than in the only previous high resolution study of the band [A. Mellouki, J. Vander Auwera, and M. Herman, J. Mol. Spectrosc. 193, 195–203 (1999)]. Following the correction of an offset of about +0.0008cm−1 on the band origin, this latter work was however found to provide a modelling of the ν14 band line positions almost as good as the present study, except for high J and low Kc.