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Bochum 1998 – wissenschaftliches Programm

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HK: Hadronen und Kerne

HK 7: Nuclear Moments

HK 7.4: Gruppenbericht

Montag, 16. März 1998, 14:45–15:15, E

Transient electric field gradients for measurements of nuc-
lear quadrupole moments of excited states with ps-lifetimes
+ — •K.-H. Speidel1, U. Grabowy1, H. Busch1, A. Gohla1, J. Cub2, H.-J. Wollersheim2, G. Jakob3, J. Gerber4, and M. Loewe51Institut f"ur Strahlen- und Kernphysik, Univ. Bonn, Nußallee 14-16, D-53115 Bonn — 2Gesellschaft f"ur Schwerionenforschung mbH, Planckstraße 1, D-64291 Darmstadt — 3Dept. of Phys., Rutgers Univ., USA — 4Institut de Recherches Subatomique, F-67037 Strasbourg, France — 5Sektion Phys. Ludwig-Maximilian Universit"at M"unchen, D-85748 Garching

Transient Electric Field Gradients (TEFG) have been observed for the first time in measurements of particle-gamma angular correlations of Coulomb excited nuclei in H-like ions during traversal through thick metallic targets. They arise from distortions of the 1s electrons by the wake field gradient (having a strength of 1017 V/cm2.) which is induced by the charge of the fast moving ion.
VZZ values deduced for 20Ne, 32S, 40Ar, 52Cr, 54Fe and 62Ni are found to be of the order of 1021 V/cm2 which exceed EFGs of non-cubic crystalline lattices by 3 orders of magnitude. In all these cases, the first 2+–states with lifetimes between 0.24 ps and 2.1 ps, served as probe for the quadrupole interactions during times being smaller or comparable to the lifetimes. One difficulty in these measurements is related with magnetic hyperfine interactions from the ions’ recoil into vacuum.
A test case was 32S(2+) as its quadrupole moment and lifetime provided extremely sensitive conditions. A value of VZZ=+5.3(1.3)· 1021 V/cm2 has been deduced. Similar results were obtained for the other nuclei. In all cases studied the observed interaction frequencies ω Q ∼(Q· VZZ) reflect the sign of the quadrupole moment, as VZZ has consistenly a positive sign. These results open the unique possibility to apply this technique to nuclear structure studies

[1] U. Grabowy et al., Phys. Rev. Lett. in press + supported by BMBF and DFG

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