Münster 2002 – wissenschaftliches Programm

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HK: Physik der Hadronen und Kerne

HK 20: Heavy Ions II

HK 20.6: Vortrag

Dienstag, 12. März 2002, 18:30–18:45, E

Development of an atomic clock for the fission lifetimes based on K-shell hole production — •Vladimir Kravchuk¹, Hans Wilschut¹, Ad van den Berg¹, Fabrice Fleurot¹, Mark de Huu¹, Herbert Loehner¹, and Marek Polasik² — ¹Kernfysisch Versneller Instituut Zernikelaan 25 9747 AA Groningen The Netherlands — ²Nicolas Copernicus University 87-100 Torun Poland

A program has been started to investigate the fission time scale using as a clock the lifetime of atomic K-shell holes. K x-rays of the pre-scission nucleus in coincidence with fission fragments relate directly to the fission lifetime. As a first step K- and additional L-shell ionization induced by 20 MeV/u He, C, O, and Ne beams on Ta, Pb, and Th targets, and 80 MeV/u He, C, O beams on a Pb target has been studied. K x-ray production cross sections have been measured and compared with theoretical calculations. Probabilities of creation of one additional L-shell hole, accompanying a K-shell hole, have been deduced from experimental data, using the theoretical positions and intensities of the diagram and satellite K x-ray lines, obtained from the multiconfiguration Dirac-Fock calculations. This new approach avoids explicit measurements of the L x-rays and can be applied with the use of a standard Ge detector. As a second part of our program we studied Direct Ionization. K x-ray spectra of 30 MeV/u Ne induced reaction on different targets were obtained in coincidence with the elastically scattered particles in order to determine direct K-shell ionization probabilities.