Absorption spectrum in the wings of the potassium second resonance doublet broadened by helium

TL;DR

This study measures the absorption spectrum in the wings of the potassium doublet lines broadened by helium at high temperature, revealing features that inform potential energy surface calculations for K-He interactions.

Contribution

The paper provides precise measurements of potassium line profiles broadened by helium, especially a shoulder feature, aiding future theoretical modeling of K-He molecular interactions.

Findings

Detected a shoulder-like broadening feature on the blue wing of the doublet

Measured line profiles at 900 K with high accuracy

Observed a flat absorption region between 401.8 nm and 402.8 nm

Abstract

We have measured the reduced absorption coefficients occurring in the wings of the potassium 4S-5P doublet lines at 404.414 nm and at 404.720 nm broadened by helium gas at pressures of several hundred Torr. At the experimental temperature of 900 K, we have detected a shoulder-like broadening feature on the blue wing of the doublet which is relatively flat between 401.8 nm and 402.8 nm and which drops off rapidly for shorter wavelengths, corresponding to absorption from the X doublet Sigma+ state to the C doublet Sigma+ state of the K-He quasimolecule. The accurate measurements of the line profiles in the present work will sharply constrain future calculations of potential energy surfaces and transition dipole moments correlating to the asymptotes He-K(5p), He-K(5s), and He-K(3d).