Vibrational and Electronic Dephasing Time Measurement with the Use of Temporally Incoherent Light
The dynamical properties of matter have been studied by increasing number of scientists, and information with higher time resolution is being obtained by the development of picosecond and femtosecond spectroscopies. Since picosecond light pulses were first emitted from passively mode-locked ruby laser in 1965 , continuous efforts to get shorter pulses have been made, and recently optical pulses as short as 8 fs were obtained  by the method of pulse compression of the output from a group-velocity-dispersion-compensated colliding-pulse mode-locked laser. Time-resolved coherent and conventional spectroscopies have been applied to several systems using ultrashort light pulses with pulse width of a few tens to a hundred femtoseconds. However, there are several difficulties in the study of the ultrafast phenomena using such short pulses: (i) Laser systems for the generation of ultrashort pulses are necessarily very expensive and complicated. (ii) The wavelengths of femtosecond laser pulses are limited in the region around 615–625 nm because of the lack of appropriate combination of saturable absorber and gain medium, and the tunability of each laser is generally poor. (iii) It is difficult to maintain a short pulse width in actual optical systems, since shorter pulse has broader power spectrum and suffers from dispersion broadening when it passes through ordinary dispersive or nonlinear materials.
KeywordsCellulose DMSO Chloroform Coherence Beach
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- 35.J.D.W. van Voorst, D. Brandt, and B.L. van Hensbergen, in Technical Digest of Topical Meeting on Ultrafast Phenomena, (1986)Google Scholar