The states 1^1\Sigma^+_u, 1^1\Pi_u and 2^1\Sigma^+_u of Sr_2 studied by Fourier-transform spectroscopy

TL;DR

This study uses Fourier-transform spectroscopy to precisely analyze the electronic states of Sr₂, revealing deviations from theoretical models and identifying state couplings and perturbations in the molecule.

Contribution

It provides detailed potential energy curves for specific Sr₂ states and compares them with ab initio calculations, highlighting discrepancies and state interactions.

Findings

Precise potentials up to 2000 cm^{-1} above the bottom.

Large deviations from ab initio calculations for 1^1\,Sigma^+_u.

Weak perturbations and strong couplings observed in certain states.

Abstract

A high resolution study of the electronic states 1^1\Sigma^+_u and 1^1\Pi_u which belong to the asymptote 4^1D + 5^1S and of the state 2(A)^1\Sigma^+_u, which correlates to the asymptote 5^1P + 5^1S, is performed by Fourier-transform spectroscopy of fluorescence progressions induced by single frequency laser excitation. Precise descriptions of the potentials up to 2000 cm^{-1} above the bottom are derived and compared to currently available ab initio calculations. Especially for the state 1^1\Sigma^+_u large deviations are found. Rather weak and local perturbations are observed for the states 1^1\Pi_u and 2^1\Sigma^+_u, while a strong coupling of the state 1^1\Sigma^+_u to the component \Omega=0^+_u of the state 1^3\Pi_u, which belongs to the asymptote 5^3P + 5^1S, is indicated.