Person:

Doyle, John

The collision-induced Zeeman relaxation rate for collisions of CaF X2Σ (v00 = 0) with 3He is measured to be ΓZ = (7.7 + 5.4/ − 2.5) × 10−15 cm3 /s at 2 K. This rate is a direct measurement of the influence of spin-rotation coupling on Zeeman relaxation in the first rotational level of CaF. The relationship of this rate to known molecular constants is consistent with recent theory of cold molecular collisions and outlines the 2Σ molecules conducive to magnetic trapping.

We have magnetically trapped and evaporatively cooled atomic molybdenum. Using a cryogenic helium buffer gas, 2×10^10 molybdenum atoms are loaded into a magnetic trap at an initial temperature of 500 mK. We measure a molybdenum inelastic rate constant of gin = (1.2±0.6)×10^−12cm^3s^ −1 for the initial conditions after loading. The molybdenum atoms are cooled by adiabatic expansion and forced evaporation to 200 mK.

Elastic and inelastic collision-rate constants of 52Cr in the temperature range of 20 mK to 1 K are inferred from the evaporative cooling of buffer gas loaded atomic chromium. Using a model that describes the dynamics of the trapped chromium cloud during evaporation, we find gel= 2.15 +2.5,−1.2 10−10 cm3 / s and gin = 1.36 +1.2,−0.7 10−12 cm3 / s, consistent with theory but in disagreement with previously reported measurements.

Metastable helium is buffer gas cooled, magnetically trapped, and evaporatively cooled in large numbers. 1011 4 He* atoms are trapped at an initial temperature of 400 mK and evaporatively cooled into the ultracold regime, resulting in a cloud of 2± 0.5 109 atoms at 1.4± 0.2 mK. Efficient evaporation indicates low collisional loss for 4 He* in both the ultracold and multi-partial-wave regime, in agreement with theory.