New Technique for the Measurement of Reaction Constants of Photochemically Produced Nah

The diffusion of NaH molecules in H2 gas and its reactive loss mechanism are described. The temporal behaviour of photochemically produced NaH in the reactive Na(3p)-H2(v″ = 2;3) collision system was observed by means of resonant coherent anti-Stokes Raman scattering (RECARS). A simple diffusion model, presented in this article, applies well in the lower pressure region (0 mbar). The binary diffusion constant for NaH molecules in H2, D0 = 0:7 cm2/s at 1 atm and 273 K, was determined. At higher pressures (up to 900 mbar), where the influence of diffusion decreased, an unexpectedly rapid decay of the NaH signal is observed. From this time behaviour we identify a new NaH loss mechanism and shown for the first time by means of time resolved CARS that this reaction can be described by a second-order rate equation in NaH.