Direct Photoassociative Formation of Ultracold KRb Molecules in the Lowest Vibrational Levels of the Ground State

TL;DR

This paper demonstrates a continuous method for creating ultracold KRb molecules in their lowest vibrational states via direct photoassociation, utilizing a novel resonant coupling to enhance production efficiency.

Contribution

It introduces a new resonant coupling mechanism between specific molecular energy levels to improve the formation rate of ultracold KRb molecules in the ground vibrational state.

Findings

Achieved a production rate of 5,000 molecules/sec for the ground vibrational state.

Discovered a resonant coupling between specific excited molecular levels.

Successfully formed ultracold KRb molecules in the lowest vibrational levels.

Abstract

We report continuous direct photoassociative formation of ultracold KRb molecules in the lowest vibrational levels $(v"=0 -10)$ of the electronic ground state $(X ^1\Sigma^+)$, starting from $^{39}$K and $^{85}$Rb atoms in a magneto-optical trap. The process exploits a newfound resonant coupling between the $2(1), v'=165$ and $4(1), v'=61$ levels, which exhibit an almost equal admixture of the uncoupled eigenstates. The production rate of the $X^1\Sigma^+$ ($v"$=0) level is estimated to be $5\times10^3$ molecules/sec.