Knowledge Bank

A procedure for measurement of fluorescence lifetimes using a narrow-band pulsed laser is presented which is qualified by its subnanosecond time resolution. In this fluoremeter, molecular fluorescence is excited by a pulsed dye $laser1$ and the fluorescence decay data are processed by a computer-controlled waveform digitizer. This system is to be employed with best advantage for a single ro-vibronic study of molecular relaxation process in the excited gas phase molecule. The fluoresecent sample and a light-scattering suspension are studied in successive measurements. The observed time-evolution of fluorescence decay is routinely analysed to get the best-fitted decay rate in terms of a convolution integral. The system performance are demonstrate by sample results of lifetime measurements for a popular dye solution (DODCI, Rh6G). The method is applied to the lifetime measurement in the visible system, $B3\pi (O+)\leftarrow X1\Sigma +$, of distomic ICI molecule, with a preliminary lifetime determination of 1.2 ns for the single ro-vibrational (v' = 3, P(35)) predissociation.