OPTIMIZATION OF A PULSE LASER SPECTROMETER FOR THE MEASUREMENT OF THEKINETICS OF SINGLET OXYGEN O-2(DELTA(1)(G)) DECAY IN SOLUTION

A simple sensitive pulse laser spectrometer to measure the kinetics of singlet oxygen decay in solution is described. It utilizes a NdYag la ser for pulse excitation of the O-1(2) photosensitizers perinaphthenon e and Rose Bengal or eosine at 355 nm and 532 nm, respectively. Single t oxygen phosphorescence is detected by a germanium diode, to which co llimated phosphorescence light is directed by concave and parabolic mi rrors via a pair of Fresnel lenses and an infrared interference filter . The O-1(2) transient decays are monitored using a Hewlett Packard di gitizing oscilloscope and a PC computer. The excellent sensitivity of this spectrometer allows us to easily observe O-1(2) decay (1 mu s res olution) after a single pulse of laser excitation, which is important for quenching measurements of chemical substrates that react readily w ith O-1(2). The small sample volume (0.1 ml) prepared in quartz tubes permits fast and inexpensive data acquisition for the determination of O-1(2) quenching rate constants in most solvents.