VIBRATIONALLY INDUCED FORMATION OF NAH IN THE NA(3P)-2 COLLISION SYSTEM - RATE-EQUATION MODEL AND COMPARISON WITH EXPERIMENTAL RESULTS(H)

Nonlinear optical methods (four-wave-mixing spectroscopy) and linear a bsorption spectroscopy were used to analyze the reaction of sodium hyd ride (NaH) in the Na(3p)+ H-2 collision system.-To explain the reactio n pathway, we developed a rate equation model which reproduced the dyn amic and kinetic behavior of the Na(3p)+ H-2 system at all parameter v alues chosen in the cell experiment. The concentration of the reactant s was varied and different excitation lasers with short (10 ns) and lo ng (1.5 mu s) pulses were used. The model describes the chemical forma tion of NaH by the following two-step process: (I) Na(3p)+ H-2-->Na(3s )+ H-2(upsilon ''>0), and (II) Na(3p)+ H-2(upsilon ''>0) --> NaH+H. Th e rate constant of the final step, which represents a collision of a N a(3p) atom with a vibrationally excited H-2 molecule (upsilon ''>0), i s determined for the first time as k = (1.1 +/- 0.3) x 10(-9) cm(3) s( -1). (C) 1998 American Institute of Physics.