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A method for "on-line" determination of beam-jet overlaps; application to cluster fragmentation studies (2000)

Wohrer, K. ; Chabot, M. ; Fossé, R. ; [et al.]

[S.l.] : American Institute of Physics (AIP)

Review of Scientific Instruments 71 (2000), S. 2025-2032

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ISSN: 1089-7623

Source: AIP Digital Archive

Topics: Physics , Electrical Engineering, Measurement and Control Technology

Notes: We present a method for determination of beam-jet overlaps in crossed-beam experiments (particle beam–molecular beam). This quantity, necessary for extracting absolute values of collisional cross sections, is difficult to determine and most of the experimentalists use normalization procedures or rely on calculations. In the present method, essentially experimental, there is no need to know precisely either the beam or local jet characteristics, the only requirement being to have a beam smaller than the jet's dimensions. It is an "on-line" method, then allowing beam-jet overlaps under the exact conditions of the experiments to be determined; in that respect, it may be a useful tool for all accelerator-based experiments. We have shown, through detailed experiments, that the theoretical part entering in the determination could be confidently predicted. The method was applied mostly to the determination of beam-jet overlaps in cluster-atom collision studies and in the particular conditions of a beam passing very near the jet's capillary exit. In this special situation, we could prove the applicability of the method as well. © 2000 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.1150572

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Multi-ionization cross-sections of small ionic carbon clusters by particle impact as a tool to investigate their shapes (2001)

Chabot, M. ; Fossé, R. ; Wohrer, K. ; [et al.]

Springer

The European physical journal 14 (2001), S. 5-8

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ISSN: 1434-6079

Keywords: PACS. 34.50.Fa Electronic excitation and ionization of atoms (including beam-foil excitation and ionization) – 34.50.Gb Electronic excitation and ionization of molecules; intermediate molecular states (including lifetimes, state mixing, etc.) – 34.10.+x General theories and models of atomic and molecular collisions and interactions (including statistical theories, transition state, stochastic and trajectory models, etc.) – 36.40.Mr Spectroscopy and geometrical structure of custers

Source: Springer Online Journal Archives 1860-2000

Topics: Physics

Notes: Abstract: Single, double and triple ionization cross-sections of C n + clusters in collisions with helium atoms at intermediate velocity (2.6 a.u.) have been measured ( n = 1 → 5). The relative multi-ionization cross-sections (double over single and triple over single) are first increasing with n, then decreasing when going from n = 4 to n = 5. We show, on the basis of an independent atom and electron collisional treatment, that this effect is attributable to a change in the cluster shape. The role of the cluster compactness on relative multi-ionization cross-sections is pointed out here for the first time.