Rotation-Vibration Constants for the nu1, nu22, nu24, nu22 + nu24, and Ground States in Pyrrole (12C4H5N).

We have recorded the infrared absorption spectrum of pyrrole at 0.005 cm-1 spectral resolution using a Fourier transform interferometer. The rotational analysis of the symmetric out-of-plane C-H bend 22(1)0 fundamental band at 722.132993(5) cm-1 was performed, allowing 6760 lines to be assigned. These lines were fitted simultaneously to literature data on nu1 [A. Mellouki, R. Georges, M. Herman, D. L. Snavely, and S. Leytner, Chem. Phys. 220, 311-322 (1997)] and microwave lines [G. Wlodarczak, L. Martinache, J. Demaison, and B. P. Van Eijck, J. Mol. Spectrosc. 127, 200-208 (1988)]. A set of rotation parameters was determined for the ground state in Ir and IIIr representations, together with vibration-rotation constants for the v1 = 1 and v22 = 1 vibrational states. The fine structure in the strongest of the hot bands in that range was highlighted by division, from the experimental data, of the spectrum of the 22(1)0 band, computed using the vibration-rotation parameters. The rotational assignment of 930 lines in the strongest hot band was performed. The 22(1)024(1)1 vibrational assignment is proposed, leading to x22,24 = 1.90 cm-1. The transition dipole matrix element for the 22(1)0 band is estimated to || || = 2 x 10(-4) D. Copyright 1999 Academic Press.