The C(2)$^1\Pi_u$ state in Rb$_2$. Observation and deperturbation

TL;DR

This study investigates the C(2)¹Πᵤ state in rubidium dimers using high-resolution spectroscopy, analyzing perturbations and deriving potential energy curves through coupled-channels deperturbation.

Contribution

It provides the first detailed deperturbation analysis of the C(2)¹Πᵤ state in rubidium dimers, including potential energy curves and interaction parameters.

Findings

Reproduced ~3000 spectral lines with 0.07 cm⁻¹ accuracy.

Identified and modeled interactions with nearby electronic states.

Derived potential energy curves and off-diagonal matrix elements.

Abstract

We report a systematic study of the C(2)$^1\Pi_u$ electronic state in rubidium dimer, observed in polarization labelling spectroscopy experiment through the C $\leftarrow$ X$^{1}\Sigma^{+}_{g}$ transitions recorded under rotational resolution in two isotopologues $^{85}$Rb$_2$ and $^{85}$Rb$^{87}$Rb. Regularity of the vibrational progressions was distorted by numerous interactions with the surrounding 2$^1\Sigma^{+}_{\mathrm{u}}$, 2$^3\Pi_{\mathrm{u}}$ and 3$^3\Sigma^{+}_{\mathrm{u}}$ states. Deperturbation was performed by coupled-channels analysis taking into account spin-orbit and rotational interactions. Potential energy curves and parameters describing the off-diagonal matrix elements were determined as functions of internuclear distance. About 3000 line frequencies from the present study are reproduced with a standard deviation of 0.07 cm$^{-1}$, in agreement with the experimental accuracy. Along with this, the model is consistent with all high resolution experimental data on the involved electronic states, available in the literature.