Narrow-line magneto-optical trap for europium

TL;DR

This paper demonstrates a narrow-line magneto-optical trap for europium atoms, achieving high atom numbers, low temperatures, and high densities, advancing cold atom research with lanthanides.

Contribution

It introduces a novel narrow-line MOT for europium, combining metastable and ground-state atom cooling for improved trapping efficiency.

Findings

Captured up to 4.7×10^7 atoms

Achieved atom temperature of 6 μK

Reached peak density of 2.2×10^11 cm^{-3}

Abstract

We report on the realization of a magneto-optical trap (MOT) for europium atoms using a narrow-line cooling transition with a natural linewidth of 97 kHz. Our starting point is continuous capturing and cooling of optically pumped metastable europium atoms. We have employed simultaneous MOT for the metastable and ground-state atoms. The trapped metastable atoms are successively pumped back to the ground state and then continuously loaded to the narrow-line MOT, where up to $4.7\times10^7$ atoms are captured. A spin-polarized sample at a temperature of $6\,\mathrm{\mu K}$ and with a peak number density of $2.2\times10^{11}\,\mathrm{cm^{-3}}$ is obtained through the compression process, resulting in a phase space density of $3\times10^{-5}$.