Observation of quantum diffractive collisions using shallow atomic traps

TL;DR

This study measures how shallow atomic traps lose atoms due to quantum diffractive collisions with background gas, revealing the importance of trap depth in understanding collision dynamics and cross sections.

Contribution

It provides experimental and theoretical analysis of trap loss rates in shallow traps caused by quantum diffractive collisions, highlighting the role of trap depth in collision measurements.

Findings

Loss rate varies with trap depth due to quantum diffractive collisions.

Differences in loss rates between MOT and magnetic traps are due to potential depth.

Trap loss rate dependence can be used to infer differential cross sections.

Abstract

We present measurements and calculations of the trap loss rate for laser cooled Rb atoms confined in either a magneto-optic or a magnetic quadrupole trap when exposed to a room temperature background gas of Ar. We study the loss rate as a function of trap depth and find that copious glancing elastic collisions, which occur in the so-called quantum-diffractive regime and impart very little energy to the trapped atoms, result in significant differences in the loss rate for the MOT compared to a pure magnetic trap due solely to the difference in potential depth. This finding highlights the importance of knowing the trap depth when attempting to infer the total collision cross section from measurements of trap loss rates. Moreover, this variation of trap loss rate with trap depth can be used to extract information about the differential cross section.