Absolute absorption on the potassium D lines:theory and experiment

TL;DR

This paper combines experimental measurements and theoretical modeling of potassium D line absorption in thermal vapor, validating the ElecSus model and demonstrating its use for thermometry and decay rate measurements.

Contribution

It provides the first experimental validation of ElecSus for an atom with small hyperfine splitting and introduces a new method for precise decay rate measurement.

Findings

Excellent agreement between theory and experiment with rms errors of ~10^{-3}

Demonstrated ElecSus as an effective thermometry tool

Predicted a new decay rate measurement technique with ~3 kHz precision

Abstract

We present a detailed study of the absolute Doppler-broadened absorption of a probe beam scanned across the potassium D lines in a thermal vapour. Spectra using a weak probe were measured on the 4S $\rightarrow$ 4P transition and compared to the theoretical model of the electric susceptibility detailed by Zentile et al. (2015) in the code named ElecSus. Comparisons were also made on the 4S $\rightarrow$ 5P transition with an adapted version of ElecSus. This is the first experimental test of ElecSus on an atom with a ground state hyperfine splitting smaller than that of the Doppler width. An excellent agreement was found between ElecSus and experimental measurements at a variety of temperatures with rms errors of $\sim 10^{-3}$. We have also demonstrated the use of ElecSus as an atomic vapour thermometry tool, and present a possible new measurement technique of transition decay rates which we predict to have a precision $\sim$ 3 kHz.