A fast sampling time-resolved ESR spectrometer for photoflash experiments with gases

Describes an electronic instrumentation system which has been designed to study the photochemistry of gas reactions. The equipment can be used for time-resolved ESR dissociation-recombination experiments which produce transient paramagnetic atoms, and also for one- way photochemical reactions with paramagnetic intermediates. One novel feature is a logarithmic sampling mode which is useful when looking for ESR transients of unknown duration. Both the logarithmic and the normal linear sampling modes use short (1 mu s) sampling times. A discussion of signal-to-noise ratio as sampling times approach zero is presented, and prefiltering requirements for both the linear and the logarithmic sampling modes are considered. The equipment is being used both for Zeeman and Stark transition electron resonance studies.