Steric proficiency of polar 2Σ molecules in congruent electric and magnetic fields

We examine the eigenenergies, spatial orientation, and alignment of polar (2)Sigma molecules subject to congruent static electric and magnetic fields. In the presence of a magnetic field only, certain pairs of Zeeman states with opposite parity intersect. Introducing a congruent electric field connects such states, thereby creating avoided crossings and a first-order Stark effect which can strongly orient the states. Since this effect, termed "steric proficiency,'' operates over a narrow range of magnetic field strength, with amplitude determined by the electric dipole interaction, it should find use both for state selection and as a diagnostic tool for assigning spectral transitions. Other aspects are illustrated by strategies suggested for some prospective applications. These include a way to test whether formation of the A (2)Sigma(+) excited electronic state of NaO in the Na + O-3 reaction results from the orientation dependence of electron transfer, and techniques to enable the ground (2) Sigma(+) states of RbO and CsO, produced by reacting NO2 with alkali atoms, to be loaded into a magnetic trap.