Lamb-dip spectroscopy of the C−N stretching band of methylamine by using frequency-tunable microwave sidebands of CO2 laser lines

Abstract

Lamb-dip spectroscopy of the C−N stretching band of methylamine has been systematically extended to P-, Q-, and R-branch by using microwave sidebands of a large number of CO2 laser lines as frequency-tunable infrared sources in a sub-Doppler spectrometer. Lamb-dip signals of more than 150 spectral lines have been observed with a resolution of 0.4 MHz and their frequencies have been precisely measured with an accuracy of ±0.1 MHz. More than 30 closed combination loops have been formed, which unambiguously confirm the assignments. For over 150 vibrational excited levels in 27 substates, refined term values have been determined and expanded in J(J + 1) power-series to determine the substate origins and the effective rotational constants. For transitions with Aa torsion-inversion symmetry in torsional state υt = 0, 57 K-doublet lines displaying asymmetry splittings have been observed and the splitting constants for levels with K = 1, 2, and 3 in the excited states have been determined. Our results provide accurate experimental information for spectroscopic studies of the interesting vibrational perturbations and intermode interactions related to the C−N stretching mode, directly support astronomical surveys, and are very relevant in practice to identification and frequency determination of the CO2-laser-pumped far-infrared laser lines of methylamine.

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“…The peak at 2869 cm −1 is assigned to the stretching vibration of C-H bonds. The absorption bands at 1150 and 1025 cm −1 are ascribed to the asymmetric stretching and skeletal stretching vibration of C-O-C [ 24 , 25 ]. Obviously, these FT-IR characteristic absorption peaks of Arg-CS are very similar to those of CS, suggesting that the combination of Arg and CS does not destroy the skeleton structure of CS.…”

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“…29 Prema rezultatima istraživanja koje su proveli Beard i sur. 30 parcijalno dvostruke s n(C−N) = 1,5 je 134 pm (pirazin), 47 dvostruke 127 pm (metanimin) 48 i trostruke veze 115 pm (cijanovodik). 20 Primjenom jedn.…”

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