Prospects for high-resolution microwave spectroscopy of methanol in a Stark-deflected molecular beam

TL;DR

This paper investigates high-resolution microwave spectroscopy of methanol in a Stark-deflected molecular beam to improve measurements related to fundamental physical constants, proposing a feasible experimental setup with high accuracy.

Contribution

It presents a detailed analysis of Stark shifts, trajectory simulations, and ionization efficiency, demonstrating the potential for highly precise microwave measurements of methanol.

Findings

Stark shift calculations for methanol rotational levels

Simulation of molecular trajectories in a Stark-deflected beam

Assessment of femtosecond laser ionization efficiency

Abstract

Recently, the extremely sensitive torsion-rotation transitions in methanol have been used to set a tight constraint on a possible variation of the proton-to-electron mass ratio over cosmological time scales. In order to improve this constraint, laboratory data of increased accuracy will be required. Here, we explore the possibility for performing high-resolution spectroscopy on methanol in a Stark-deflected molecular beam. We have calculated the Stark shift of the lower rotational levels in the ground torsion-vibrational state of CH3OH and CD3OH molecules, and have used this to simulate trajectories through a typical molecular beam resonance setup. Furthermore, we have determined the efficiency of non-resonant multi-photon ionization of methanol molecules using a femtosecond laser pulse. The described setup is in principle suited to measure microwave transitions in CH3OH at an accuracy below 10^{-8}.