Europhys. Lett.
Volume 67, Number 4, August 2004
Page(s) 586 - 592
Section Nuclear physics
Published online 01 August 2004
Europhys. Lett., 67 (4), pp. 586-592 (2004)
DOI: 10.1209/epl/i2004-10089-5

Population inversion of nuclear states by a Penning trap mass spectrometer

K. Blaum1, 2, D. Beck2, G. Bollen3, P. Delahaye1, C. Guénaut4, F. Herfurth2, A. Kellerbauer1, H.-J. Kluge2, D. Lunney4, S. Schwarz3, L. Schweikhard5 and C. Yazidjian2

1  CERN, Physics Department - 1211 Genève 23, Switzerland
2  GSI - Planckstraße 1, 64291 Darmstadt, Germany
3  NSCL, Michigan State University - East Lansing, MI 48824-1321, USA
4  CSNSM-IN2P3-CNRS - 91405 Orsay-Campus, France
5  Institute of Physics, Ernst-Moritz-Arndt-University - 17487 Greifswald, Germany

(Received 7 April 2004; accepted 2 June 2004)

According to the energy-mass equivalence, E=mc2, excited long-lived nuclear states, so-called isomers, are distinguished from the ground state by their additional mass. The ultra-high accuracy provided by Penning traps now allows to weigh nuclear excitation energies. With the on-line Penning trap mass spectrometer ISOLTRAP, we have developed a mass-separation procedure of sufficient resolving power to isolate particles of a selected isomeric state from an ensemble delivered from the radioactive beam facility ISOLDE at CERN, first demonstrated for $\chem{{}^{68}Cu}$. The resulting unique form of ion ensembles opens up a large variety of new nuclear-physics experiments. Mass excesses of -65567.0(1.6) $\un{keV}$ for the 1+ ground state and -64850.3(1.5) $\un{keV}$ for the 6- isomeric state have been determined.

21.10.Dr - Binding energies and masses.
07.75.+h - Mass spectrometers.
21.10.-k - Properties of nuclei; nuclear energy levels.

© EDP Sciences 2004