  We study anisotropic thermalization in dilute gases of microwave shielded
polar molecular fermions. For collision energies above the threshold regime, we
find that thermalization is suppressed due to a strong preference for forward
scattering and a reduction in total cross section with energy, significantly
reducing the efficiency of evaporative cooling. We perform close-coupling
calculations on the effective potential energy surface derived by Deng et al.
[Phys. Rev. Lett. 130, 183001 (2023)], to obtain accurate 2-body elastic
differential cross sections across a range of collision energies. We use
Gaussian process regression to obtain a global representation of the
differential cross section, over a wide range of collision angles and energies.
The route to equilibrium is then analyzed with cross-dimensional
rethermalization experiments, quantified by a measure of collisional efficiency
toward achieving thermalization.
