Ultracold quantum dynamics: spin-polarized K + K_2 collisions with three identical bosons or fermions

TL;DR

This study develops a new potential energy surface and performs quantum calculations to analyze ultracold K + K2 collisions, revealing that vibrational quenching rates are high and not suppressed for fermions, contrasting with high vibrational state molecules.

Contribution

The paper introduces a new potential energy surface and quantum dynamical calculations for ultracold K + K2 collisions involving bosons and fermions, highlighting differences from high vibrational state molecules.

Findings

Quenching rates are well described by classical models above 0.1 mK.

Ultracold quenching rates are not suppressed for fermionic atoms.

Vibrational quenching exceeds elastic scattering rates at ultralow temperatures.

Abstract

We have developed a new potential energy surface for spin-polarized K($^2$S) + K$_{2}(^3\Sigma^+_u)$ collisions and carried out quantum dynamical calculations of vibrational quenching at low and ultralow collision energies for both bosons $^{39}$K and $^{41}$K and fermions $^{40}$K. At collision energies above about 0.1 mK the quenching rates are well described by a classical Langevin model, but at lower energies a fully quantal treatment is essential. We find that for the low initial vibrational state considered here ($v=1$), the ultracold quenching rates are {\it not} substantially suppressed for fermionic atoms. For both bosons and fermions, vibrational quenching is much faster than elastic scattering in the ultralow-temperature regime. This contrasts with the situation found experimentally for molecules formed via Feshbach resonances in very high vibrational states.