High intensity pulsed analyzing light sources for nano- and micro-second absorption spectrophotometry

Abstract

This paper describes in detail the construction, circuitry, and performance of high intensity pulsed analyzing light sources with 500 W xenon short arc lamps, used in nano- and micro-second absorption spectrophotometry. Operation is based on discharge of a rectangular current capacitor bank with sag correction, and initiated by firing a single high current thyristor. Light pulses of about 1 msec duration with a flat top, where the intensity is constant within 0.2% during 100 μsec, are produced. Data on the ratio of the light intensity as a function of wavelength in the pulsed mode as compared to continuous operation are presented as measured in the actual absorption spectrophotometer used in pulse radiolysis experiments. At a wavelength of 600 nm the pulsed intensity is found to be linear with capacitor bank voltage. Routine operation of an Osram XBO 450 W lamp in an Oriel C-60–50 housing with the capacitor bank charged to 110 V gives typically a pulsed to continuous intensity ratio of 16 at 600 nm and 40 at 300 nm. Approximately 20 times higher light intensities have been obtained by using a Varian Eimac xenon illuminator 500 × 10 R.