OBSERVATION OF PICOSECOND TRANSIENT RAMAN-SPECTRA BY ASYNCHRONOUS FOURIER-TRANSFORM RAMAN-SPECTROSCOPY

Asynchronous Fourier transform (FT) Raman spectroscopy with 100 picose cond time resolution has been developed. A signal-processing assembly required for time-resolved and transient Raman measurements consists o f a picosecond Nd:YLF laser system, a gate circuit, and a low-pass fil ter, and it can be attached to any conventional continuous-scan FT-Ram an spectrophotometer, The principle of signal processing employed in t his method is almost the same as that of asynchronous pulsed-laser-exc ited FT-Raman spectroscopy, This method does not require synchronizati on between Raman excitation by probe laser pulses and sampling by the analog-to-digital converter, Transient Raman spectra have been obtaine d from the first excited singlet state of three anthracene derivatives in cyclo-hexane solutions and photoexcited poly(p-phenylenevinylene) [(C6H4CH=CH)(n)] by using 351 mn light (pulse width approximate to 70 ps) for photoexcitation and 1053 nm light (pulse width approximate to 100 ps for Raman excitation.