Characterizing ultra-narrow momentum of atoms by standing-wave light-pulse sequences

TL;DR

This paper introduces a method using standing-wave light-pulse sequences to precisely characterize ultra-narrow atomic momentum distributions, enabling accurate temperature calibration of ultracold gases including BECs.

Contribution

It provides a detailed analysis of beam splitting mechanisms and analytical expressions for momentum distribution measurement, applicable to both classical gases and BECs.

Findings

Analytical expressions for diffraction order populations.

Method valid for ultra-cold temperatures down to 100 pK.

Demonstrates phase space evolution via Wigner function.

Abstract

We propose a method to characterize the ultra-narrow momentum distribution of atomic gases by employing a standing-wave light-pulse sequences beam-splitter. The mechanism of beam splitting is analyzed in detail, and the influence of a finite-width momentum distribution on the population of each diffraction order is given. The temperature of ultracold atomic gases can be calibrated by measuring the ratio of population in different diffraction orders after double standing-wave light-pulses. We obtain analytical expressions for two typical cases, and demonstrate phase space evolution in the whole process by using the Wigner function. This method is valid for both classical atomic gas and Bose-Einstein condensates, and it is suited for temperature measurement on the space ultra-cold atomic physics platform, in which the ultra-narrow momentum distribution of atomic gas is on the order of 100pK or even lower.