Collisional de-excitation in a quasi-2D degenerate Bose gas

TL;DR

This study investigates collisional de-excitation in a quasi-2D Bose gas, revealing suppressed decay rates due to reduced dimensionality, with detailed characterization of vibrational state dynamics and decay processes.

Contribution

It provides the first detailed experimental analysis of vibrational de-excitation in a quasi-2D Bose-Einstein condensate, demonstrating dimensionality-induced suppression of collisional decay.

Findings

Decay rates are suppressed compared to 3D systems.

Vibrational energy levels are identified via ring diameters.

Lifetimes of excited vibrational states are measured.

Abstract

We separate a Bose-Einstein condensate into an array of 2D sheets using a 1D optical lattice, and then excite quantized vibrational motion in the direction normal to the sheets. Collisions between atoms induce vibrational de-excitation, transferring the large excitation energy into back-to-back outgoing atoms, imaged as rings in the 2D plane. The ring diameters correspond to vibrational energy level differences, and edge-on imaging allows identification of the final vibrational states. Time dependence of these data provides a nearly complete characterization of the decay process including the energies, populations, and lifetimes of the lowest two excited vibrational levels. The measured decay rates represent a suppression of collisional de-excitation due to the reduced dimensionality, a matter wave analog to inhibited spontaneous emission.