How does flash photolysis help scientists study short-lived chemical intermediates?

Flash photolysis is an experimental technique used to study short-lived chemical intermediates that are formed during fast photochemical reactions. Developed by R.G.W. Norrish and Sir George Porter, the method allows scientists to observe and identify transient molecular fragments that exist for only a brief period.12

The process involves two distinct steps:
* Dissociation: A sample of gas or liquid is subjected to an intense, short burst of light (lasting microseconds or milliseconds), which causes the absorbing compound to break down into short-lived molecular fragments.12
* Identification: A second, less intense flash of light is used to probe the sample, allowing scientists to identify these intermediates through spectrophotometry.1

By monitoring the evolution of absorption spectra over time, researchers can track the behavior of these transient species. While early experiments relied on flash lamps, modern techniques utilize lasers to achieve much higher time resolution, enabling the study of processes occurring on the femtosecond scale.2