Time-resolved interferometric laser

An interferometric method was first used by Porter and Topp [1, 92] to perfonn a time-resolved absorption experiment with a -switched ruby laser in the 1960s. The nonlinear crystal in the autocorrelation apparatus shown in figure B2.T2 is replaced by an absorbing sample, and then tlie transmission of the variably delayed pulse of light is measured as a fiinction of the delay This approach is known today as a pump-probe experiment the first pulse to arrive at the sample transfers (pumps) molecules to an excited energy level and the delayed pulse probes the population (and, possibly, the coherence) so prepared as a fiinction of time. 

Figure 4. Three-dimensional representation of the time-resolved data near 8 = 0 as they appear following one interferometric scan. The sampling interval employed was 1.2656 jxm, corresponding to a Nyquist wavenumber of 3950.7 cm 1. Selection of an interferogram at any time delay following the photolysis laser pulse is possible, and is shown here for t = 150/is. Reproduced with permission from Ref. 37.

One of the designed photolabile triazene polymers (Scheme 8) was selected to test whether a different behavior can be detected for these materials. In this report, decomposition dynamics of the photosensitive triazene polymer film upon intense XeF excimer laser irradiation is studied by applying the nanosecond interferometric technique with a newly improved optical setup. On the basis of the revealed morphological dynamics as well as the obtained time-resolved transmission and reflectance, the ablation mechanism and the dynamics of the triazene polymer film are discussed in detail. 

Ulness D J, Stimson M J, Kirkwood J C and Albrecht A C 1997 Interferometric downconversion of high frequency molecular vibrations with time-frequency-resolved coherent Raman scattering using quasi-cw noisy laser light C-H stretching modes of chloroform and benzene J. Rhys. Chem. A 101 4587-91... 

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