Ultracold fermionic Feshbach molecules are promising candidates for exploring quantum matter with strong $p$-wave interactions; however, their lifetimes were measured to be short. Here we characterize the $p$-wave collisions of ultracold fermionic ${}^{23}\mathrm{Na}{}^{40}\mathrm{K}$ Feshbach molecules for different scattering lengths and temperatures. By increasing the binding energy of the molecules, the two-body loss coefficient reduces by three orders of magnitude, leading to a second-long lifetime 20 times longer than that of ground-state NaK molecules. We exploit the scaling of elastic and inelastic collisions with the scattering length and temperature to identify a regime where the elastic collisions dominate over the inelastic ones, allowing the molecular sample to thermalize. Our results provide a benchmark for four-body calculations of molecular collisions and pave the way for investigating quantum many-body phenomena with fermionic Feshbach molecules.

• Received 24 February 2023
• Accepted 18 April 2023

DOI:https://doi.org/10.1103/PhysRevA.107.053322

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Open access publication funded by the Max Planck Society.

Published by the American Physical Society