A flash-photolysis electron spin resonance spectrometer

A technique is described for recording the electron spin resonance spectra of paramagnetic species existing at different stages of a photochemical reaction. The sample is placed in the cavity of an electron spin resonance spectrometer and irradiated with 100 μs flashes of ultra-violet light, at the rate of one flash per 15 seconds. The presentation is obtained by six parallel sampling channels that sample the output from the spectrometer at different intervals after each flash. The field of the magnet is swept slowly and the output from each sampling channel describes a different spectrum. As an example of the use of the spectrometer results are presented for the flash-photolysis of benzophenone in an isopropanol and water solution. The sensitivity is compared with that of some other techniques.