Chemiluminescent reactions of the IVA elements: dihalide formation

Earlier work on chemiluminescent beam-gas reactions of Si, Ge, and Sn with F2 [W. J. Rosano and J. M. Parson, J. Chem. Phys. 79, 2696 (1983)] is extended to reactions with Br2, I2, ClF3, SF4, and SF6. In all of these new systems electronic emission is attributable exclusively to IVA dihalide products. Reaction of Sn with the diatomics most likely procedes by a two-step mechanism involving a highly vibrationally excited Sn monohalide intermediate. The polyatomic reactants, on the other hand, yield IVA difluoride products in a single collision. Radiation of the dihalides from the 3B1 state to the ground 1A1 state is consistent with the thermochemistry of these mechanisms. The dependence of the emission on the IVA atom velocity shows that energy barriers to reaction are small or nonexistent.