Effect of pressure and temperature on the H-atom tunneling in solid phase chemical reactions. The acridine/fluorene system

In this paper the influence of temperature and pressure on the rate constant of photosensibilized tunneling of a hydrogen atom in an 'acridine-fluorene' system is considered. The influence of various types of vibrations on the temperature dependence of the hydrogen transfer rate constant is studied. Published experimental data on the temperature and pressure dependence are treated in terms of a modified theory of radiationless transitions. The reduction of equilibrium intermolecular distances and the frequency increase of the promotive modes under the effect of the applied external pressure are taken into account. The H/D isotope effect of the investigated reaction is considered. The literature data for the dependence 'volume vs. pressure' in aromatic single crystals are utilized for the interpretation of experimental results. (C) 1998 Elsevier Science B.V. All rights reserved.