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 J.l-m 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 10 3 _10 5 with comparable energy resolution. Measurements are performed on the dissociative charge exchange of Hi with Mg atoms. In the range of 7.2-10.2 eV 17 discrete energies are observed due to the predissociation of the c 3 1Tu state in H2 and presumably also the c 11Tu state.

State-resolved translation energy distributions for NCO photodissociation

“…2͒ or the time and position sensing ͑TPS͒ microchannel plate ͑MCP͒ detector assembly based on the concept developed by de Bruijn and Los. 35 The TPS detector yields the positions of both photofragments and difference in their arrival times; our implementation of this detector has been described in detail elsewhere. 28,29 An aluminum strip is placed across the center of the detectors in order to prevent undissociated parent radicals from striking the MCPs.…”

Predissociation and autoionization of triplet Rydberg states in molecular hydrogen

“…Still, these Rydberg states have been studied starting from the long-lived metastable c 3 ⌸ u Ϫ state, which has an excitation energy of Ϸ11.6 eV, and which may be produced by low energy electron impact or using chargetransfer collisions between molecular hydrogen ions and alkali atoms, such as sodium, rubidium, or cesium. 9,10 For these reasons, most studies in triplet hydrogen have focussed on the d-gerade Rydberg series. [11][12][13] To the best of our knowledge no triplet np-ungerade Rydberg series have been detected.…”

Multifragmentation of molecules and clusters

“…However, most work so far has concentrated on the observation of individual reaction products without further attention to the correlated behaviour of the remaining fragments (cf., e.g., [2] and references therein). Exceptions can be found in dissociation studies of some diatomic molecules where the correlation of both fragments has been studied in detail (e.g., [3][4][5]) and in the Coulomb explosion imaging (CEI) of high energetic molecular ions (e.g., [1]) where all fragments from a particular explosion are detected in coincidence. In the work to be reported here, we use a similar approach to establish coincidences between low-energy fragments of a neutral molecule.…”