Time-resolved Spectroscopy - Transient-absorption Spectroscopy

Transient-absorption Spectroscopy

Transient-absorption spectroscopy is an extension of absorption spectroscopy. Here, the absorbance at a particular wavelength or range of wavelengths of a sample is measured as a function of time after excitation by a flash of light. In a typical experiment, both the light for excitation ('pump') and the light for measuring the absorbance ('probe') are generated by a pulsed laser. If the process under study is slow, then the time resolution can be obtained with a continuous (i.e., not pulsed) probe beam and repeated conventional spectrophotometric techniques.

Examples of processes that can be studied:

• Optical gain spectroscopy of semiconductor laser materials.
• Chemical reactions that are initiated by light (or 'photoinduced chemical reactions');
• The transfer of excitation energy between molecules, parts of molecules, or molecules and their environment;
• The behaviour of electrons that are freed from a molecule or crystalline material.