Collisional properties of sympathetically cooled $^{39}$K

TL;DR

This paper demonstrates sympathetic cooling of potassium-39 with rubidium-87 to near 1 microkelvin and measures its elastic cross section, providing new experimental data on its collisional properties.

Contribution

First direct measurement of the elastic cross section of $^{39}$K below 50 microkelvin using a novel magnetic trap.

Findings

Elastic cross section measurement of $^{39}$K yields a triplet scattering length of -51(7) Bohr radii.

Sympathetic cooling achieved down to 1 microkelvin in a new magnetic trap.

Results agree with previous spectroscopic measurements.

Abstract

We report the experimental evidence of the sympathetic cooling of $^{39}$K with $^{87}$Rb down to 1 $\mu$K, obtained in a novel tight confining magnetic trap. This allowed us to perform the first direct measurement of the elastic cross section of $^{39}$K below 50 $\mu$K. The result obtained for the triplet scattering length, $a_T = -51(7)$ Bohr radii, agrees with previous results derived from photoassociation spectra and from Feshbach spectroscopy of $^{40}$K.