Laser-cooling Cadmium Bosons and Fermions with Near Ultraviolet Triplet Excitations

TL;DR

This paper demonstrates laser cooling and trapping of all stable cadmium isotopes, including fermions, using near-ultraviolet triplet excitations with simple magnetic field requirements, avoiding deep UV transitions.

Contribution

It introduces a novel laser cooling scheme for cadmium using UVA triplet states, enabling efficient trapping with minimal magnetic fields and no need for additional repumping.

Findings

Successfully trapped all 8 stable cadmium isotopes.

Observed isotope shifts for key transitions in cadmium.

Measured the $^{114}$Cd transition frequency as 830,096,573(15) MHz.

Abstract

Cadmium is laser-cooled and trapped with excitations to triplet states with UVA light, first using only the $67\,$kHz wide $326\,$nm intercombination line and subsequently, for large loading rates, the $25\,$MHz wide $361\,$nm $\,^3P_2$$\,\rightarrow\,$$\,^3D_3$ transition. Eschewing the hard UV $229\,$nm $^1S_0$$\,\rightarrow$$\,^1P_1$ transition, only small magnetic fields gradients, less than $6\,$G$\,$cm$^{-1}$, are required enabling a 100\% transfer of atoms from the $361\,$nm trap to the $326\,$nm narrow-line trap. All 8 stable cadmium isotopes are straightforwardly trapped, including two nuclear-spin-$\frac{1}{2}$ fermions that require no additional repumping. We observe evidence of $^3P_2$ collisions limiting the number of trapped metastable atoms, report isotope shifts for $^{111}$Cd and $^{113}$Cd of the $326\,$nm $^1S_0$$\,\rightarrow$$\,^3P_1$, $480\,$nm $^3P_1$$\,\rightarrow$$\,^3S_1$, and $361\,$nm $^3P_2$$\,\rightarrow$$\,^3D_3$ transitions, and measure the $^{114}$Cd 5s5p$\,^3P_2$$\,\rightarrow\,$5s5d$\,^3D_3$ transition frequency to be $830\,096\,573(15)\,$MHz.