Rovibrational dynamics of the strontium molecule in the A^1\Sigma_u^+, c^3\Pi_u, and a^3\Sigma_u^+ manifold from state-of-the-art ab initio calculations

TL;DR

This study employs advanced ab initio methods to accurately compute potential energy curves, coupling elements, and transition moments for the strontium dimer's excited states, enabling detailed rovibrational analysis and predictions for experimental validation.

Contribution

The paper provides the first comprehensive ab initio calculations of potential energy curves, coupling matrix elements, and transition moments for key states of the strontium dimer, improving upon previous theoretical models.

Findings

Potential energy curves agree with experimental data for the (1)0_u^+ state.

Calculated rovibrational levels match observed spectra semi-quantitatively.

Predicted positions and lifetimes of Feshbach resonances aid future experiments.

Abstract

State-of-the-art ab initio techniques have been applied to compute the potential energy curves for the electronic states in the A^1\Sigma_u^+, c^3\Pi_u, and a^3\Sigma_u^+ manifold of the strontium dimer, the spin-orbit and nonadiabatic coupling matrix elements between the states in the manifold, and the electric transition dipole moment from the ground X^1\Sigma_g^+ to the nonrelativistic and relativistic states in the A+c+a manifold. The potential energy curves and transition moments were obtained with the linear response (equation of motion) coupled cluster method limited to single, double, and linear triple excitations for the potentials and limited to single and double excitations for the transition moments. The spin-orbit and nonadiabatic coupling matrix elements were computed with the multireference configuration interaction method limited to single and double excitations. Our results for the nonrelativistic and relativistic (spin-orbit coupled) potentials deviate substantially from recent ab initio calculations. The potential energy curve for the spectroscopically active (1)0_u^+ state is in quantitative agreement with the empirical potential fitted to high-resolution Fourier transform spectra [A. Stein, H. Knoeckel, and E. Tiemann, Eur. Phys. J. D 64, 227 (2011)]. The computed ab initio points were fitted to physically sound analytical expressions, and used in converged coupled channel calculations of the rovibrational energy levels in the A+c+a manifold and line strengths for the A^1\Sigma_u^+ <-- X^1\Sigma_g^+ transitions. Positions and lifetimes of quasi-bound Feshbach resonances lying above the ^1S + ^3P_1 dissociation limit were also obtained. Our results reproduce (semi)quantitatively the experimental data observed thus far. Predictions for on-going and future experiments are also reported.