Elastic and inelastic collisions of ²Σ molecules in a magnetic field

We calculate the cross sections for elastic scattering and Zeeman relaxation in binary collisions of molecules in the ro-vibrational ground state of a ²Σ electronic state and the Zeeman state with the electron spin projection M_S=1/2 on the magnetic field axis. This is the lowest-energy state of ²Σ molecules confined in a magnetic trap. The results are averaged over calculations with multiple molecule - molecule interaction potentials, which yields the expectation intervals for the cross sections and the elastic-to-inelastic cross section ratios. We find that the elastic-to-inelastic cross section ratios under conditions corresponding to trapped molecular ensembles at T sim 10^-3 K exceed 100 for the majority of ²Σ molecules. The range of ²Σ molecules expected to be collisionally unstable in magnetic traps at T < 10^-3 K is limited to molecules with the spin-rotation interaction constant γ_{rm SR} > 0.5 cm^-1 and the rotational constant B_e < 4 cm^-1.