The Laser Flash Photolysis technique provides one of the most effective methods for studying by direct measurement the reactions of transient species such as radicals, excited states or ions, in chemical and biological systems.
The use of a laser for sample excitation gives the technique the specificity of single wavelength excitation and nanosecond time resolution, and the high reproducibility of pulsed light output from the analysing source permits routine generation of time-resolved spectra over these timescales. Finding wide application in chemical research, Laser flash photolysis has been used increasingly in the area of bioinorganic reaction mechanisms, for example, studies on electron transport in cytochromes or ligand binding by haem containing proteins. More exotic applications involving the Laser Flash Photolysis technique have recently included studies on the conformational changes of functional proteins that occur during the course of their activity.
The flash photolysis concept is very simple. A short pulse of light is used to interact with a sample that has been placed in the optical path of a spectrometer. The result of this interaction can be either a transient absorption or an emission process. The changes in detector signal taking place following laser excitation may be due to a variety of processes such as electronic excitation producing a triplet state, cleavage of a molecule producing radicals, electron transfer, molecular rearrangement etc...
The laser interaction with the sample often results in irreversible changes and this necessitates sample replacement for each individual measurement (customers often use a flow-through sample arrangement to achieve this). In addition, many measurements are required to be done in the absence of oxygen and so the samples either need to be degassed using the classical freeze-pump-thaw method or by purging using an inert gas. However, some reactions processes are reversible such as the classic experiment comprising the photolysis of carboxyhaem, where green light (532nm, Nd:YAG 2nd harmonic) is used to displace carbon monoxide allowing the study of adduct interaction with the haem molecule.
Applied Photophysics has been supplying laser flash photolysis instruments since 1973. The experience gained during this period has resulted in the LKS80 spectrometer which offers both ease of use and flexibility with respect to special configurations.