Speaker
Description
Over the last two decades, a drift of interest in molecular science has steered towards the creation and manipulation of ultracold molecules. The intricate internal structure of molecules due to the presence of rotational and vibrational degrees of freedom attracts more attention because of their application in quantum simulation, precision measurement, and ultracold chemistry. To date, a limited number of studies on the collisional properties of ultracold molecules are available, where ultracold noble gas molecules are still largely unexplored.
This project explores ultracold molecular interactions and collisional dynamics involving metastable noble gas helium molecules in a spin-polarized triplet state, $^3\Sigma^+_u$. We use state-of-the-art ab initio quantum chemistry methods to understand the interactions between two metastable He$_2$ molecules by calculating the potential energy surfaces (PESs) both in their ground and excited electronic states. Our analysis identifies a global minimum with $D_{2d}$ symmetry having a depth of 3100 cm$^{-1}$, supporting multiple ro-vibrational bound states. The PES for this global minimum undergoes curve crossings with other symmetry states arising from the excited electronic state.
Once we finish a complete multidimensional PES for the helium tetramer, our next aim is to calculate the full-dimensional quantum scattering calculations for He$_2$ $(^3\Sigma^+_u)$ + He$_2$ $(^3\Sigma^+_u)$ collisions to measure the scattering length and to investigate state-selective energy-transfer processes. The metastable He$_2$ is a light system with four electrons, its PES and scattering properties can be computed with high accuracy. On top of the immediate importance of He$_2$ ($^3\Sigma^+_u$), this molecule is an ideal system for laser cooling and a perfect candidate for precision measurements. Interactions and cold collisions between He$_2$ molecules are also useful for evaporative cooling, analyzing the formation of the Bose-Einstein condensate of metastable helium molecules.
[1] S. L. Cornish, M. R. Tarbutt, and K. R. A. Hazzard, Nat. Phys, 20, 730, (2024).
[2] T. E. Wall, J. Phys. B: At. Mol. Opt. Phys, 49, 243001, (2016).
[3] T. Karman, M. Tomza, and J. P{\'e}rez-R{\'\i}os, Nat. Phys, 20 722, (2024).
