Time resolved molecular spectroscopy using high power solid state lasers in pulse transmission mode. A re-examination of the Sn← S1 spectra of naphthalene and anthracene

A nanosecond laser spectrometer consisting of a 3nsec ruby/Nd PTM laser, fast detection system and high brightness analysing source is described. An analysis of the geometry considerations is given for crossed beam and collinear arrangement. The excited-state absorption spectra of naphthalene in 3MP at 85°K and 293°K from 14000 to 30000 cm^?1 are given. The results provide a direct method to evaluate the quantum yields for fluorescence φ_f and intersystem crossing φ_T. Also the excited-state absorption spectra of anthracene in PMM from 16000 to 26000 cm^?1 and in 3MP from 26000 to 36000 cm^?1 are reported.     

Generation,stabilization, and amplification of subpicosecond pulses

A sync-pumped cw dye laser system has been used to produce subpicosecond pulses. Pulses as short as 0.7 ps, assuming a single-sided exponential pulse shape, were observed. A set of experiments was performed to investigate the origin and effects of noise in the sync-pumped system. A digital and an analog feedback loop have been designed to optimize the pulse width. The noise has been lowered by 10 dB for frequencies up to 10 kHz; long-term drift is also controlled by this method. A four-stage dye laser amplifier, pumped by a Nd:YAG laser which operates at a 10-Hz repetition rate, is synchronized electronically to the dye-laser picosecond pulses. A gain of 3×10⁶ has been achieved.This work was supported by the Joint Services Electronics Program     

SPECTRAL PROPERTIES OF (ISO)ALLOXAZINES IN THE VAPOUR PHASE

Abstract— Spectral properties of alloxazine and isoalloxazine derivatives were determined at high temperatures in the vapour phase. In comparison with spectra observed in solution, vapour phase spectrometry gives primary photophysical properties of the isolated chromophore. Fluorescence lifetimes in the vapour phase range from <0.5 to 18 ns. There is some indication that an intramolecular complex can exist between the isoalloxazine moiety and its aliphatic side chain carrying a polar (hydroxyl) group. Direct photodissociation of the molecule in its first electronically excited singlet state is not very probable.