Rovibrational and rotational spectroscopy of the ν2=1, ν5=1, and ν3=2 levels of 13CH3 37Cl

Abstract

Fourier-transform infrared (IR) spectra between 1235 and 1680 cm−1 and millimeter wave spectra between 198 and 455 GHz of monoisotopic 13CH3 37Cl have been recorded and analysed simultaneously, taking into account all Coriolis, α-resonance, and l-type interactions in the polyad of the ν2=1, ν5=1 and ν3=2 levels. Several α-resonances (Δ k = ±2,Δ l = ∓ 1) generating perturbation-allowed transitions have been assigned both in the rovibrational and rotational spectra. This enabled us to determine accurately and independently A 0= 5.2057128 (72) cm−1, = 8.3968 (105)×10−5 cm−1, and even = 3.95 (38)× 10−9 cm−1. With 52 upper state parameters varied, more than 5300 IR wavenumbers and 162 rotational frequencies pertaining to the excited vibrational states were fitted within their experimental accuracy. The textbook example of a first-order Coriolis resonant crossing between the A and E fundamental vibrational levels (ν2=1 and ν5=1) is discussed in detail with implications for the structures of the corresponding parallel ν 2 and perpendicular ν 5 bands and their intensity perturbations.