DYNAMICAL STEREOCHEMISTRY ON SEVERAL ELECTRONIC STATES - A COMPUTATIONAL STUDY OF NA-ASTERISK-2(H)

The orbital control of stereochemistry is discussed with special refer ence to the Na (3p P-2) + H-2 collision. As seen by H-2, the p orbital of the electronically excited Na atom is like a quadrupole, which may or may not lock along the molecular axis. Quantum mechanically, varia tions in the alignment of the orbital represent changes in the electro nic state of the system and so dynamical methods which allow for such interstate transitions must be used. A new, time dependent quantum mec hanical method for propagating the wave function on several electronic states is used to study these interstate transitions. Particular atte ntion is given to the question of orbital following. The computational method is fully quantum mechanical but it uses a basis set which take s full account of the classical motion on any given electronic state w hile the solution of the Schrodinger equation addresses the electronic -state-changing transitions. We pay specific attention to the orbital alignment for both cold and rotationally warm H-2 and for low and high impact parameters throughout the course of the collision. It is concl uded that orbital locking is not necessarily instantaneous and can lag behind the faster nuclear motion, including the (fast) rotational mot ion of H-2.