A MULTICHANNEL TRANSIENT SPECTRUM ANALYSER FOR ABSORPTION CHANGES MEASUREMENT WITH ONE MICROSECOND RESOLUTION

A custom-designed photometer for recording flashlight-induced transient absorbance spectra with microsecond time resolution in the wavelength range from 350 to 800 nm with 0.5 nm resolution is reported. The apparatus is equipped with two 600 ns half-width pulse (output = 400 mJ) tunable dye lasers for double-flash analysis and an optical multichannel analyser having a silicon intensified target detector. Measuring light from a tungsten-halogen lamp is passed through the sample, dispersed into a spectrum and focused on the head of the detector. A transient spectrum is measured over a range of 330 nm simultaneously by applying high voltage to the detector for the desired interval. The delay from the actinic flash to applying the high voltage can be controlled electronically. Distortion caused by scattering of the actinic flash under optimal conditions is negligible within 1.5 is after the flash peak. Detector linearity reaches about 10⁴ and a noise level of less than ±0.005A can be achieved without data accumulation. This apparatus is applicable not only to transparent samples but to turbid ones with 100 μs resolution.