Perspectives for coherent optical formation of strontium molecules in their electronic ground state

TL;DR

This paper investigates methods to coherently form ultracold strontium molecules in their ground state using optical Feshbach resonances and short-pulse photoassociation, analyzing their applicability and transition pathways.

Contribution

It provides a comparative analysis of optical Feshbach resonance and short-pulse photoassociation techniques for ultracold strontium molecule formation.

Findings

Optical Feshbach resonances are suitable for tightly trapped atom pairs.

Short-pulse photoassociation can be used in both shallow and tight traps.

Transitions near the intercombination line are also considered.

Abstract

Optical Feshbach resonances [Phys. Rev. Lett. 94, 193001 (2005)] and pump-dump photoassociation with short laser pulses [Phys. Rev. A 73, 033408 (2006)] have been proposed as means to coherently form stable ultracold alkali dimer molecules. In an optical Feshbach resonance, the intensity and possibly frequency of a cw laser are ramped up linearly followed by a sudden switch-off of the laser. This is applicable to tightly trapped atom pairs. In short-pulse photoassociation, the pump pulse forms a wave-packet in an electronically excited state. The ensuing dynamics carry the wave-packet to shorter internuclear distances where, after half a vibrational period, it can be deexcited to the electronic ground state by the dump pulse. Short-pulse photoassociation is suited for both shallow and tight traps. The applicability of these two means to produce ultracold molecules is investigated here for $^{88}$Sr. Dipole-allowed transitions proceeding via the $B^1\Sigma_u^+$ excited state as well as transitions near the intercombination line are studied.