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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Articles you may be interested inEtching of SiO 2 film by synchrotron radiation in hydrogen and its application to lowtemperature surface cleaning Role of surface adsorption in the surfaceinduced alignment of nematic liquid crystals on evaporated SiO films

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Scattering of (10–400 eV) O+, O+2 , C+, CO+, and CO+2 ions from a Pt(100) surface has been studied. Below 100 eV, the peak position of the angular distribution for survival ions was shifted parallel to the surface, and the lobe width was very narrow in comparison with noble-gas ions. This suggests that surface trapping due to chemical interaction takes place at very low energies. The importance of collisional neutralization at high energies is demonstrated by the result that the yields of reactive ions decrease steeply with increasing incident energy. The scattering ion yields of O+ and O+2 ions, especially, were very low, being less than 1/100 and 1/10 of those of nitrogen ions, respectively. These results show that a chemical interaction effect is significant for the scattering of oxygen ions.