The potential energy surfaces (PES) of 16 electronic states for the Mo + H2 reaction are studied in two modes of collisions, namely collinear (Cmu) and perpendicular (C,) modes, using the complete active space MCSCF (CASSCF) followed by multireference singles + doubles configuration interaction (MRSDCI) method. The effect of spin-orbit coupling on the ground state of MoX, is also addressed by use of the relativistic CI (RCI) method. In the insertion mode (C,), the.'S ground state of Mo has to

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... rmount a barrier of 89 kcal/mol to insert with H2 to form the linear 7Xg+ MoH, state, while the b5D (4d55s') state of Mo inserts spontaneously into H, to form the bent 5B, MoH2 ground state (Re = 1.67 A, Be = 116'). The other electronic states of Mo such as a5S, a5D, etc. insert into H2 with small barriers while a3P, a3D, and a % states insert into H2 spontaneously. The 7AI and 5B2 curves cross at 8 N 35' which should provide for a channel for 7S insertion in the Landau-Zener model. In the collinear (C-J mode of collision, the Mo(~S) atom forms only a weak complex with H2 while some of the quintet and triplet states form a stronger bond with H2. Thus Mo reacts in the insertion mode more readily than the collinear mode. Mulliken population analyses and dipole moment analyses reveal considerable ionic character of the Mo-H bonds in MoH2.