Hyperfine structure of methanol lines at 25 GHz

TL;DR

This study presents high-resolution laboratory measurements of methanol's hyperfine structure at 25 GHz, revealing discrepancies with existing quantum models and highlighting the need for model refinement.

Contribution

It provides detailed experimental hyperfine data for methanol lines at 25 GHz and compares them with quantum-mechanical simulations, identifying significant inconsistencies.

Findings

Observed hyperfine splitting patterns differ from simulations.

Current models do not accurately reproduce line shape morphologies.

Refinement of quantum-mechanical models is necessary.

Abstract

High-dispersion (channel width 0.015 km s^-1) laboratory spectroscopy of the torsion-rotation lines J_2 - J_1 (J = 2 - 6) in the ground torsional state (vt = 0) of the E-type methanol demonstrates multicomponent hyperfine splitting patterns at 25 GHz. The observed patterns are compared with simulations of CH3OH emission lines based on ab initio quantum-mechanical models. A substantial disparity between the laboratory and simulated patterns is revealed. The observed morphology of the line shapes is not reproduced in the model profiles. The found inconsistency requires further refinement of the current quantum-mechanical models to fit the observed hyperfine splitting patterns at 25 GHz.