Apparatus for investigating fast chemical reactions by optical detection

In an apparatus for investigating the course of fast chemical reactions by optical detection, said reactions being initiated in a chemical system by an external perturbation using a high-voltage pulse, said apparatus comprising a sample cell holding a liquid sample of said chemical system, means performing said perturbation, monochromatic illumination means, a reference beam divider, at least one light path transversing said sample cell, and optical detection means including at least two photodetectors operatively connected to a signal processing unit provided with individual input amplifiers, the improvement wherein said photodetectors are arranged as individual photodetector heads in operative position, said photodetector heads comprising photomultiplier tube, dynode switching network, current-to-voltage transducer and housing and shielding means, said input amplifiers having differential input, each of said photodetector heads being connected to said signal processing unit by a shielded multi-lead cable and multi-lead connector, said cable comprising an inner shielded signal cable connected to said differential input, further comprising supply leads for operating said photomultiplier tube and said current-to-voltage transducer, and also respective photodetector head to the housing of said signal processing unit.