A large magneto-optical trap of cadmium atoms loaded from a cryogenic buffer gas beam

TL;DR

This paper demonstrates rapid loading of a cadmium atom magneto-optical trap using a cryogenic helium buffer gas beam and deep-UV laser cooling, achieving high density and mitigating photoionization losses.

Contribution

It introduces a novel method for efficiently loading high-density cadmium MOTs from a cryogenic buffer gas beam using deep-UV transitions, with dynamic detuning to reduce photoionization losses.

Findings

Loaded up to 1.1×10^7 cadmium atoms in 10 ms

Achieved a peak density of 2.5×10^11 cm^-3

Measured the photoionization cross section of the $^1P_1$ state

Abstract

We demonstrate rapid loading of a magneto-optical trap (MOT) of cadmium atoms from a pulsed cryogenic helium buffer gas beam, overcoming strong photoionization losses. Using the $ ^1S_0 \rightarrow{} ^1P_1 $ transition at 229 nm, we capture up to $ 1.1(2) \times 10^7$ $^{112}$Cd atoms in 10 ms, achieving a peak density of $2.5 \times 10^{11}$cm$^{-3}$ and a phase-space density of $ 2 \times 10^{-9} $. The large scattering force in the deep ultraviolet enables Zeeman slowing within 5 cm of the trap, yielding a capture velocity exceeding 200 m/s. We measure the MOT trap frequency and damping constant, and determine the absolute photoionization cross section of the $^1P_1 $ state. Photoionization losses are mitigated via dynamic detuning of the trapping light's frequency, allowing efficient accumulation of multiple atomic pulses. Our results demonstrate the benefits of deep-UV (DUV) transitions and cryogenic beams for loading high-density MOTs, especially for species with significant loss channels in their main cooling cycle. The cadmium MOT provides a robust testbed that benchmarks our DUV laser cooling system and establishes the foundation for trapping and cooling polar AlF molecules, which share many optical and structural properties with Cd.