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 rovibrational ground state of a (2)Sigma 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 (2)Sigma molecules confined in a magnetic trap. The results are averaged over calculations with multiple molecule-molecule interaction potentials, which yield 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 similar to 10(-3) K exceed 100 for the majority of (2)Sigma molecules. The range of (2)Sigma molecules expected to be collisionally unstable in magnetic traps at T < 10(-3) K is limited to molecules with the spin-rotation interaction constant gamma(SR) > 0.5 cm(-1) and the rotational constant B-e < 4 cm(-1).