In order to investigate effects of high magnetic fields on the primary process of photochemical reactions such as hydrogen abstraction and electron transfer reactions, a laser flash photolysis apparatus equipped with a pulse magnet was developed. The magnet system consisted of a home-made solenoid coil(9.74mH)and a capacitor bank(4mF, 5kV, 50kJ). The full width at half maximum of the pulsed magnetic field was ca. 13ms and its maximum strength was 20T at room temperature. The laser flash photolysis system was composed of a pulse laser and a Xe arc lamp as excited and probe light sources, respectively, and a streak scope. The advantage of this pulsed magnetic field-laser flash photolysis apparatus is that transient absorption and emission of the short-lived radical intermediates can be measured in solution at room temperature even upon single laser pulse. Magnetic fic1d effect (MFE) upon photolysis of benzophenone in aqueous Brij35 surfactant solution was studied by using this new apparatus. As increasing the magnetic field intensity, the decay rate of the radical pair was retarded below 2T, while it was accelerated at 2-14T.
The inversion of MFE was ascribed to anisotropy of electron g-value of the radicals.