F. Meissner

Spin alignment of43Sc produced in the fragmentation of 500 MeV/u46Ti

In the fragmentation of 500 MeV/u46Ti the spin alignment of43mSc (I=19/2−, T1/2=473 ns) fragments was observed by the Time Dependent Perturbed Angular Distribution (TDPAD) method. The measurement was performed for different cuts in the longitudinal momentum distribution. A positive spin alignment of about 35% was observed in the center and a negative alignment of about 15% in the wing of the distribution. For the different cuts the relative production of the 19/2− state was measured. In the wing of the distribution the isomeric ratio N(19/2−)/total43Sc is about 15 times larger than in the center. The results of this pilot experiment are discussed in the frame of a shell-model.

Study of the β decays of 37Ca and 36Ca

Abstract The β-delayed proton and γ-ray emission of 37Ca and 36Ca was studied at the projectile fragment separator at GSI Darmstadt. In the 37Ca study, the β-delayed γ decay was observed for the first time, and the half-life was redetermined, under essentially background-free conditions, as 181.1 ± 1.0 ms. The surprisingly high Γ γ Γ p values found for proton-unbound states in 37K drastically reduce former discrepancies between the Gamow-Teller strength values B(GT) measured in the 37Ca β decay and those deduced from the 37Cl(p,n)37Ar mirror reaction. Our data provide evidence, on a level of 1.6 standard deviations, for isospin-mixing of the lowest T = 3 2 level in 37K. In the 36Ca study, a complete β decay scheme, including the β-delayed proton emission into the ground and first excited states of 35Ar as well as the β-delayed γ decay, was measured for the first time. The 36Ca half-life was remeasured with improved accuracy to be 102 ± 2 ms. Our data exclude a 1+ assignment for two near-thrd states in 36K that could be important resonances in 35Ar(p,γ) reactions of astrophysical interest. The B(GT) distributions in 37,36Ca decays are compared to results obtained from large-scale sd shell-model calculations.

Spectroscopic investigation of 164,168Ta, 166,W and 164,165Hf

Abstract Using reactions induced by beams of 36 Ar and 40 Ar in targets of 133 CsCI and 136 BaF 2 , the half-lives of 164,168 Ta, 166 W, and 164,165 Hf were measured to be 14.9 (2) s, 2.0 (l) min, 18.8 (4) s, 111 (8) s, and 76 (4) s, respectively. The β-decay of 166 W is reported for the first time, yielding an α-decay branch of 0.03 (1)%. Decay schemes were derived and are discussed by comparison with nuclear structure calculations.

β-decay of37Ca

Abstract The β-decay of 37Ca has been studied. The half-life was remeasured with improved precision to be 181.1 ± 1.0 ms, and β-delayed γ-rays were observed for the first time. The surprisingly high Γ γ Γ p values for proton-unbound states in 37K drastically reduce former discrepancies between the Gamow-Teller strength values B(GT) measured in the 37Ca β-decay and those deduced from the 37Cl(p,n)37Ar mirror reaction.

Gamow-Teller strength in the β-decay of 36Ca

Abstract The β-decay of 36 Ca has been studied at the projectile fragment separator at GSI Darmstadt. The measured Gamow-Teller strength function B (GT), deduced from the observed β-delayed proton- and γ-emission and from the measured half-life of 102(2) ms, is compared to results obtained from large-scale sd -shell model calculations. A systematic underestimation of the measured strength by the theory is found.

Isomerism in neutron-deficient iridium isotopes alpha- and beta-decay studies of 171–175Ir

Abstract The α- and β-decays of 171–175Ir were measured in 141Pr(36Ar, xn) reactions. New α-rays and α-coincident γ-rays were found for 171–175Ir, giving evidence for isomerism in these nuclei. The measured α- and β-decays of 171–175Ir are interpreted in terms of single-particle nuclear structure.

Half-life and α-ray energy of146Sm

Up-to-date α-decay data of the double-even,N=84 isotones are presented, including the presently remeasured values for146Sm. For this nuclide a half-life,T1/2 =1.031 (45) ×108 y, and α-ray energy, Eα=2455(4) keV, were measured. The significance of these data for the subshell closure atZ=64 observed in α-decay is discussed.

Investigation of new neutron-rich gold isotopes203Au and205Au

Using a208Pb beam of the UNILAC accelerator at GSI we produced the new isotopes203Au and205Au and identified them by measuring theirβ-decay properties. Their half-lives were found to be 60(6)s and 31(2)s, respectively, and theQ-value of203Au was determined to beQβ=2040(60)keV. Nuclear structure information of203,205Hg was derived from this measurement. Furthermore, production cross-sections of203,205Au are given and compared to those obtained in other experiments.

Revision of the decay data of166–170Re, including new isomers167m,169mRe

The neutron-deficient rhenium isotopes166–170Re were investigated using reactions of32S with monoisotopic141Pr targets. Gamma-rays following theβ-decays of166–169Re were measured for the first time. Four newα-rays with energies of 4.70,4.83, 4.87, and 5.02 MeV were detected in addition to the known 5.50, 5.26, and 5.06 MeVα-rays. Alpha-decaying isomer pairs were discovered in167Re and169Re. The measured half-lives are 2.3(2)s for166Re, 3.4(4)s and 6.2(5)s for167Re, 4.4(1)s for168Re, 8.1(5)s and 16.3(8)s for169Re, and 9.2(2)s for170Re. The nuclear structure is discussed in terms of single-particle states.

Investigation of the new isotope 172Ho and of 174Er

Abstract In multinucleon-transfer reactions between an 11.6 MeV u 136 Xe beam and enriched 186 W targets the decay of the new isotope 172 Ho was observed at the GSI on-line mass separator. For 172 Ho, the half-life was measured to be 25(3) s and a decay scheme is proposed on the basis of γγ-coincidence data. The decay of 3.1 (3) min 174 Er was reinvestigated. The decay schemes are discussed within level systematics and macroscopic-microscopic model calculations.