How does an inert atmosphere (say Ar or N2) affect the photolysis or photodissociation, specifically of PbI2? Or other compounds in general? Context: I recently did some measurement under Ar, where I expected to see the formation of metallic Pb, and surprisingly did not see any. Meanwhile, the same measurement under vacuum did see metallic Pb.
I should also add, while the mean free path is very different in the two situations (atmosphere vs vacuum), I am not entirely sure why that would prevent the decomposition.
Well, a rather trivial answer would be that collisions of the excited, dissociative state created by the laser excitation redistributes the excess energy into kinetic energy of the buffer gas atoms, thus preventing the dissociation. I an extreme case , in a solid matrix, this is the so called cage effect...We performed these kind of experiments in the eighties for CH3Br dissociated by an excimer laser on several substrates if you are interested to take a look : F. L. Tabarés, E.P. Marsh, G.A. Bach y J.P. Cowin "Laser Photofragmentation and Photo-Desorption of Physisorbed CH3Br on LiF" J. Chem. Phys., 86, 738-744 (1987).
Regards
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