Fourier Transform Microwave and Millimeter-Wave Spectroscopy of Bromoiodomethane, CH₂BrI

Stéphane Bailleux (1) , Denis Duflot (2) , Keisuke Taniguchi (3) , S. Sakai (3) , Hiroyuki Ozeki (3) , W. C. Bailey (4) , Tomohito Obakayashi (5)

1 PhLAM - Laboratoire de Physique des Lasers, Atomes et Molécules - UMR 8523
2 PCMT - Physico-Chimie Moléculaire Théorique
3 Department of Environmental Science
4 Chemistry-Physics Department
5 Graduate School of Science and Technology

Bromoiodomethane, CH₂BrI, is a molecule of natural origin emitted in significant amount into the marine boundary layer. It can easily be decomposed by solar radiation, releasing Br and I atoms in the troposphere, which in turn impacts the atmospheric chemistry. Spectroscopy is an invaluable tool to monitor species present in the atmosphere. Since no high-resolution spectroscopic studies are available for this dihalomethane, we have investigated the rotational spectra of the two bromine isotopologues of CH₂BrI in its vibrational ground state in the microwave and millimeter-wave regions. Transitions of b-type have been recorded by Fourier transform microwave spectroscopy below 25 GHz while both a- and b-type spectral lines have been measured below 230 GHz. Observed transitions correspond to energy levels with J ≤ 132 and Ka ≤ 14. Molecular constants including those describing the nuclear quadrupole coupling tensors for ⁷⁹Br, ⁸¹Br, and ¹²⁷I were accurately determined from the least-squares analysis of a total of 1873 distinct transition frequencies (of which 943 belong to the CH₂⁷⁹BrI isotopologue). An experimental (r₀) structure of the title species has been derived from the two sets of rotational constants.

Domaines: Chimie-Physique [physics.chem-ph]

Stéphane Bailleux, Denis Duflot, Keisuke Taniguchi, S. Sakai, Hiroyuki Ozeki, et al.. Fourier Transform Microwave and Millimeter-Wave Spectroscopy of Bromoiodomethane, CH₂BrI. Journal of Physical Chemistry A, 2014, 118, pp.11744. ⟨10.1021/jp510119e⟩. ⟨hal-01231004⟩