Measurement of the loss rate coefficient for Rb-Rb collisions via Quantum diffractive universality

The loss rate of a magnetically-confined cold atomic ensemble is dominated by collisions with background particles at room temperature in the vacuum environment. For a single background species of density n, this rate can be written as Γ =n〈σv〉, where the loss rate coefficient〈σv〉depends on the magnetic trap depth U. For sufficiently shallow traps, the loss rate follows a single universal curve which we have previously reported for van der Waals interactions [New J. Phys. 21 102001 (2019), Metrologia 57 025015 (2020), Metrologia 58 022101 (2021)]. This description is defined by a single, experimentally determined parameter〈σtotv〉, the velocity-averaged total cross-section, which sets the loss rate coefficient at zero trap depth and the scale over which it varies, the quantum diffractive energy U_d. Here, we present loss rate measurements of Rubidium in a magnetic trap in the presence of a background, room temperature Rubidium vapour. This admits further verification by comparing loss rates using ⁸⁷Rb or ⁸⁵Rb as the trapped species. As U_d for these collisions is small, we compare the theoretically predicted and experimentally measured loss rate curves over a wide range of the scaled energy parameter U/U_d.