The high-resolution infrared spectrum of pyrrole between 900 and 1500 cm-1 revisited

The Fourier transform gas-phase infrared spectrum of pyrrole, C4H5N, has been recorded with a resolution of ca. 0.003 cm(-1) in the 900-1500 cm(-1) spectral region. Four fundamental bands, nu(8)(A(1); 1016.9 cm(-1)), nu(23)(B-2; 1049.1 cm(-1)), nu(7)(A(1); 1074.6 cm(-1)), nu(20)(B-2; 1424.4 cm-(1)) and the overtone band 2 nu(16)(A(1); 962.7 cm(-1)) have been analysed using the Watson model. The nu(8) and 2 nu(16) bands are unperturbed; the nu(7) and nu(23) bands are locally perturbed, while the nu(20) band is globally perturbed by weak c-Coriolis resonance. Upper state vibrational term values, and rotational and centrifugal distortion constants, have been obtained from fits using S-reduction and I-r-representation as well as A-reduction and IIIr-representation. A set of ground state rotational and centrifugal distortion constants using A-reduction was obtained from a simultaneous fit of ground state combination differences from all five bands and previous microwave and millimetre-wave data. (C) 2008 Elsevier Inc. All rights reserved.