Spectroscopic investigation of ground state pyrrole (12C4H5N): the NH stretch Original Research Article

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 fundamental NH stretch (110) at 3530.811343(82) cm−1 was performed. A set of 13 upper state rovibrational parameters was determined, allowing the 2715 assigned rovibrational lines to be reproduced with a standard deviation of 1.3 10−3 cm−1. An attempt to record the fundamental band under slit-jet conditions is reported. The role of hot bands accompanying the series of the NH stretch excitation is investigated. Effective vibrational parameters — ω01, X011, Y111, X1,24 — are obtained. The lower level in the hot band series is unambiguously identified as the V24 = 1 level, by retrieving X1,24 independently, from other spectral data. The observation of the complex band pattern accompanying the NH series in the higher overtone range is discussed with the help of new data, recorded around the 150 band at different temperatures using intracavity laser optoacoustic spectroscopy.