A biogenic organic molecule involved in the formation of secondary organic aerosols: Microwave and millimeter-wave spectroscopy of 3-methylcatechol backed by quantum chemistry

3-methylcatechol (3MC) is a molecule of environmental interest due to its presence in the atmosphere during biomass burning events, leading to the formation of secondary organic aerosols. This paper goes one step further than the paper from A.S. Hazrah et al. (2022) [10] . A three-dimensional torsional potential energy surface was determined, confirming the existence of three rotamers for 3MC. One dimensional potential energy curves along the rotation of the methyl group were computed and fitted to estimate the barrier height in each conformer . Experiments were performed at low temperature in the microwave domain ( 2 − 20 GHz range) and, for the first time, in the millimeter-wave domain ( 70 − 110 GHz range) at T = 323 K with a specially designed heated absorption cell. The rotational linelist was fitted to provide updated spectroscopic parameters for the two 3MC conformers of lowest energies. In particular, the A − E splitting is observed in the microwave region for both conformers while in the millimeter-wave region, it is only seen for the conformer of the lowest energy.