MILLIMETER WAVE SPECTROSCOPY OF THE GROUND, FIRST AND SECOND EXCITED TORSIONAL STATES OF ACETONE

Abstract

Purpose: spectrum investigation of the lowest three torsional states of acetone (CH3COCH3 ) within the frequency ranges 34–150 and 480–620 GHz. Design/methodology/approach: New measurements were carried out using the automated millimeter wave spectrometer in the Insitute of Radio Asronomy of NASU (Kharkiv, Ukraine) and the submillimeter-wave spectrometer of PhLAM (Lille, France). The results of new measurements were fitted using a recently developed model for the molecules with two equivalent methyl rotors and C2v symmetry at equilibrium PAM_C2v_2tops program). Findings: Analysis of the acetone molecule spectrum was carried out using the new measurements for torsion–rotation transitions in the millimeter wave range belonging to the ground, first and second excited torsional states, as well as previously published data. In addition, we performed more accurate measurements of a number of previously published lines which posed some problems for previous analysis using the same model. Conclusions: The remeasurements have shown that the problems existed with spectrum description were caused by underestimated experimental error of the previously published data. The final fit uses 99 parameters to give an overall weighted root-meansquare deviation of 0.78 for the dataset consisting of 6233, 4868, and 4364 transitions with J up to 60 and Ka up to 35, belonging, respectively, to the ground, first, and second excited torsional states of the acetone molecule.

Keywords

• acetone
• millimeter wave spectrum
• methyl top internal rotation