Observation of Feshbach resonances in an ultracold gas of ${}^{52}$Cr

TL;DR

This paper reports the first observation of Feshbach resonances in an ultracold gas of ${}^{52}$Cr atoms, revealing unique resonance patterns due to the atom's electronic structure and providing precise scattering length measurements.

Contribution

It presents the first detection of collisional Feshbach resonances in an atomic species with multiple valence electrons and characterizes the scattering properties of ${}^{52}$Cr.

Findings

Observation of Feshbach resonances in ${}^{52}$Cr

Determination of scattering lengths for different spin states

Regularly-spaced resonance sequences due to zero nuclear spin

Abstract

We have observed Feshbach resonances in elastic collisions between ultracold ${}^{52}$Cr atoms. This is the first observation of collisional Feshbach resonances in an atomic species with more than one valence electron. The zero nuclear spin of ${}^{52}$Cr and thus the absence of a Fermi-contact interaction leads to regularly-spaced resonance sequences. By comparing resonance positions with multi-channel scattering calculations we determine the s-wave scattering length of the lowest $^{2S+1}\Sigma_{g}^{+}$ potentials to be $\unit[112(14)]{a_0}$, $\unit[58(6)]{a_0}$ and $-\unit[7(20)]{a_0}$ for S=6, 4, and 2, respectively, where $a_{0}=\unit[0.0529]{nm}$.