Calculation of the K $4s, 7s,$ and $4p$ photoabsorption near threshold

TL;DR

This paper provides a detailed calculation of potassium's photoabsorption near the ionization threshold, focusing on the Cooper minimum and comparing results with experimental data to resolve previous uncertainties.

Contribution

It introduces an improved theoretical model including core polarization effects that accurately reproduces the photoabsorption cross section around the Cooper minimum.

Findings

The model matches experimental measurements of the Cooper minimum width.

Calculated photoabsorption from excited states agrees with recent data.

Provides optical oscillator strengths for $4p\rightarrow nl$ transitions.

Abstract

We revisit the photoabsorption from the ground state of K, ending below and above the ionization threshold, with special emphasis on the shape of the photoionization cross section around the Cooper minimum. The present treatment, including core polarization effects and dynamic core polarizability matches very well the most accurate measurements resolving an older question about the width of the Cooper minimum. The photoabsorption from the excited $7s$ and $4p$ states is also calculated, along with $4p$$\rightarrow $$nl$ optical oscillator strengths, and compared with recent experimental and theoretical data.