Ultrafast Laser Spectroscopy - Ultra-fast Transient Absorption

Ultra-fast Transient Absorption

This method is typical of 'pulse-probe' experiments, where a pulsed laser is used to excite a molecule's electrons from their ground states to higher-energy excited states. A probing light source, typically a xenon arc lamp, is used to obtain an absorption spectrum of the compound at various times following its excitation. As the excited molecules absorb the second pulse, they are further excited to even higher states. After passing through the sample, the light from the arc lamp continues to an avalanche photodiode array, and the data is processed to generate an absorption spectrum of the excited state. Since all the molecules in the sample will not undergo the same dynamics simultaneously, this experiment must be carried out many times, and the data must be averaged in order to generate spectrums with accurate intensities and peaks. Unlike TCSPC, this technique can be carried out on non-fluorescent samples.