Doppler-free laser spectroscopy of buffer gas cooled molecular radicals

TL;DR

This paper presents a Doppler-free laser spectroscopy method for cold molecular radicals, enabling high-resolution spectral analysis of difficult-to-produce molecules at controlled temperatures.

Contribution

The authors develop a technique combining buffer gas cooling and Doppler-free spectroscopy to study molecular radicals with high resolution and temperature control.

Findings

Achieved 30 MHz resolution in YbF radicals

Measured magnetic hyperfine parameters accurately

Demonstrated method's applicability to various molecules

Abstract

We demonstrate Doppler-free saturated absorption spectroscopy of cold molecular radicals formed by laser ablation inside a cryogenic buffer gas cell. By lowering the temperature, congested regions of the spectrum can be simplified, and by using different temperatures for different regions of the spectrum a wide range of rotational states can be studied optimally. We use the technique to study the optical spectrum of YbF radicals with a resolution of 30 MHz, measuring the magnetic hyperfine parameters of the electronic ground state. The method is suitable for high resolution spectroscopy of a great variety of molecules at controlled temperature and pressure, and is particularly well-suited to those that are difficult to produce in the gas phase.