The C$^1\Pi_{\mathrm{u}}$ state of potassium dimer revisited: an~extensive study by polarisation labelling spectroscopy method

TL;DR

This study extensively investigates the C$^1\Pi_{u}$ state of potassium dimer using polarisation labelling spectroscopy, measuring over 1100 molecular lines, analyzing perturbations, and constructing a potential energy curve.

Contribution

It provides a detailed spectral analysis and a new potential energy curve for the C$^1\Pi_{u}$ state of potassium dimer, including perturbation insights.

Findings

Measured 1100+ rotational lines in the 22100-24100 cm$^{-1}$ range.

Localized perturbations in the lowest vibrational levels of the C state.

Constructed a potential energy curve fitting unperturbed levels.

Abstract

The polarisation labelling spectroscopy technique was applied to study the C$^1\Pi_{\mathrm{u}}$ $\leftarrow$ X$^1\Sigma^{+}_{\mathrm{g}}$ band system in potassium dimer. About 1100 new rotationally resolved molecular lines were measured in the $22100-24100$~cm$^{-1}$ spectral range. Perturbations of the lowest vibrational levels of the C state were localised and their origin discussed. A set of Dunham coefficients was deduced to fit the unperturbed levels of the C$^1\Pi_{\mathrm{u}}$ state with $0 \le v \le 38$ and $18 \le J \le 101$ and the potential energy curve of the state was constructed.