Time and position-sensitive detector for dissociative processes in fast beams

Abstract

A microchannel-plate detector has been developed to detect the time and position of two particles simultaneously. High resolution in position and timing is achieved with 100 μm FWHM and 0.5 ns FWHM, respectively. The detector is designed to measure dissociative processes of molecules in fast beams. The released kinetic energy and the direction of the associated momentum with respect to the beam direction in the center of mass can be determined directly. This method offers big advantages over the determination by means of a mass spectrometer which is common practice in the field of ’’translational spectroscopy.’’ The efficiency is increased by a factor of 103–105 with comparable energy resolution. Measurements are performed on the dissociative charge exchange of H+2 with Mg atoms. In the range of 7.2–10.2 eV 17 discrete energies are observed due to the predissociation of the c3πu state in H2 and presumably also the c1πu state.