Microcomputer Controlled Flash Photometry with Submicrosecond Resolution and Raman Spectroscopy

Abstract

The interfacing of two spectrophotometric systems to an Apple II microcomputer is described. The first is a flash photometric setup in which light flashes are formed either with a chopper wheel, or with an acousto-optic modulator which is activated by the microcomputer. Spectroscopic transients are monitored with a time resolution as short as 250 ns, by counting photon pulses into the computer's memory in the fast direct memory access mode. The formation half-times of the M₄₁₂ intermediate in the photocycle of bacteriorhodopsin were measured in H₂O and in D₂O using the characteristic Raman band of this species, and are 68 ± 2 and 300 ± 5 μs, respectively. A microcomputer-controlled Raman spectrometer, in which the Apple II is interfaced to a Spex monochromator and the photon counting electronics, is also described. These microcomputer-controlled configurations provide simple and inexpensive setups for data collection in flash photometry and Raman and fluorescence spectroscopy.