Computational, rotational and ro-vibrational experimental investigation of monodeuterated chloromethane

In the present work, a combined theoretical and spectroscopic characterization of the different isotopologues of mono-deuterated chloromethane, CH 2 DCl, has been carried out in order to provide reliable spectroscopic data to support and guide future studies. State-of-the-art ab initio calculations were performed to derive accurate predictions of equilibrium structure, rotational constants, and centrifugal distortion terms. The rotational spectra of the 13 C species have been recorded for the first time in the 250- 300 GHz frequency range and, for the two isotopologues 12 CH 2 D 35 Cl and 12 CH 2 D 37 Cl, the knowledge has been extended up to 520 GHz. The observed transitions have been analyzed with a Watson-type Hamiltonian and allowed the determination of several spectroscopic parameters, all in excellent agreement with our computed values. These new experimental and computed data, combined with the ones previously available in the literature, led to the determination of an accurate and complete semi-experimental (SE) equilibrium structure for chloromethane. The medium resolution (up to 0.1 cm -1 ) gas-phase infrared spectra of CH 2 DCl were investigated in the region 60 0-90 0 0 cm -1 . All the most important spectral features were assigned in terms of fundamental, overtone and combination bands, thus obtaining an accurate description of the vibrational structure. Several polyads involving different vibrational levels were identified and disentangled with the aid of our computed high-level hybrid force field. (c) 2023 Elsevier Ltd. All rights reserved.

Automated summary

The present work combines theoretical and spectroscopic methods to characterize the isotopologues of mono-deuterated chloromethane and provides reliable spectroscopic data for future studies. Ab initio calculations are used to accurately predict the equilibrium structure and spectroscopic parameters. The rotational spectra of different isotopologues are recorded and analyzed, and their values are in good agreement with the computed ones. The gas-phase infrared spectra of CH2DCl are investigated, and the vibrational structure is accurately described using fundamental, overtone, and combination bands.