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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. Loewe5 — 1Institut 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