The relationship between the ionic photodissociation yield and the electron donor-acceptor interaction of pyrene-quencher systems was investigated by nanosecond laser photolysis and transient photocurrent measurements. While no general relation was obtained, the chemical property of donor-acceptor pairs was found to be reflected in the yield. On the basis of the present and previous results it was concluded that the ionic photodissociation process consists of two steps, namely, the encounter collisional electron transfer and the orientational relaxation of solvents. With the latter process some other radiationless transitions depending on the chemical property compete in the dissociative excited state. It was shown in the case of pyrene-nitrile systems that an unknown quenching process, other than ionic dissociation as well as triplet formation, increases with the electron affinity.

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Irradiation by synchrotron radiation on SiO2 films induces continuous removal of this material at elevated temperatures. The photostimulated evaporation rate for a thermally grown SiO2 film increases steeply with temperature giving an activation energy of 0.7 eV. The experimental results indicate that photon-induced bond breaking assists decomposition and thermal desorption of the film. Applications to microfabrication of a line-and-space pattern and low-temperature cleaning of Si(100) surface are demonstrated.

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