NANOSECOND TRANSIENT ABSORPTION SPECTROPHOTOMETER WITH DYE-LASER PROBING AND COMPUTER CONTROL

A computer controlled apparatus for laser flash spectroscopy has been constructed. Nitrogen laser (energy 1 mJ, pulse width 1 ns) is used both for excitation of the sample and for pumping a tunable dye laser which serves as a source of monitoring light. Two different scan modes are possible: (i) a scan with a fixed wavelength of the monitoring light: the temporal evolution of the transient absorption in the range from -2 up to 100 ns can be observed by changing the length of the variable self-compensating optical delay line, or (ii) a scan with a fixed time delay: the corresponding transient absorption in the range 380-800 nm can be measured. For illustration, the transient absorption spectrum of benzophenone in methylcyclohexane, decay curves of the singlet state of benzanthracene in ethanol in the presence of a quencher, and a "negative absorption" of rhodamine B in nitriles are reported. © 1994 American Institute of Physics.