Brett Esry

One of my main efforts is studying ultracold (~nK to µK) atomic systems. Within this increasingly broad area, my group is studying three-body collisions as well as matter wave propagation through microfabricated waveguides. Neither topic has received much attention until recently, and our group is one of only a few in the world capable of carrying out the three-body collision calculations.

One of the collision processes we are interested in produces a molecule from three free atoms (three-body recombination) and is a significant loss mechanism for experiments on degenerate quantum gases. These experiments aim at understanding phenomena such as superfluidity and superconductivity, and three-body recombination must be characterized in order to interpret the experiments. In the past year, we have investigated the limits of low-energy approximations to the recombination rates. We have also looked into the other three-body processes that can occur in the experiments --- collision induced vibrational relaxation and collision induced dissociation. We found their low-energy expansion and their dependence on the scattering parameters.

Another main thrust of my work is understanding the dynamics of a molecule in an intense laser field. My group is working on ways to solve the time-dependent Schrödinger equation for this highly non-perturbative system. Even the simplest molecule H₂⁺, however, requires the solution of a six-dimensional time-dependent equation - a nontrivial job for even the biggest supercomputers. We have explored various approximation schemes on our way to a complete solution.