T. Hild

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.

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.

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.

Evidence for the Iπ=8−, K=8 isomeric state in184Hf

Using an 11.4MeV/u136Xe beam of the UNILAC accelerator of GSI and anatW target, A=184 isobars were produced and separated by using an on-line mass separator. A new isomeric state was found in184Hf. This state decays with a half-life of 48(10) s and emits three γ-rays of 73, 482, and 555 keV as well as lower-lying cascade transitions. The hindrance of the 73 keV-E1 transition with ΔK=8 is compared with those of other even-even hafnium isotopes. The half-life of184Lu was estimated to be between 15 and 25s.

Spectroscopic investigations of179Yb-decay including a Ms-isomer in Lu

The neutron-rich isotope179Yb was produced by using the multinucleon transfer reactions 11.6 MeV/u136Xe+Re and 11.4 MeV/u197Au+W. The isotope identification was achieved by combining mass-separation and decay spectroscopy. A decay scheme was constructed including a new isomeric state in179Lu with a half-life of 3.1(9) ms.

Investigation of neutron-deficient tungsten isotopes168−174W

The decays of168−174W were observed in the reactions of36Ar and40Ar beams with enriched targets of136BaF2 and138BaF2. The measured half-lives are 53(2) s, 76(6) s, 2.42(4) min, 2.38(4) min, 6.6(9) min, 6.3(4) min, and 35.3 (5) min, respectively. Decay schemes were derived from theγ− and X-ray coincidence data. Spin assignments of ground- and excited states are discussed within experimental level systematics and compared with the results of microscopic-macroscopic model calculations. Excitation energies of modeled one-quasiparticle states were found in reasonable agreement with the experimental data. Allowed unhindered beta decay from the 5/2− [523] to the 7/2− [523] configuration was identified in171W and this transition is also proposed for the decays of the even-even isotopes168, 170W.

Beta-delayed gammas and QEC-values in the decays of150m,152mHo and149Dy

Abstract150m, 152mHo, and149Dy were produced by fusion-evaporation reactions of40Ar with targets of natural indium and114Cd. Theβ-decays of the isotopes were reinvestigated with emphasis on high-excitation daughter states. The decay energies for selectedβ-transitions were measured from electron-capture to positron-decay ratios. Corrections forγ-feeding from higher-lying states were taken into account. The following QEC-values were derived for150mHo,152mHo, and149mDy of 6819 (−100+117, 6263 (−80+89), and 3914 (−52+76) keV, respectively.

Decay of the new isotope167W

Theα- and β-decay of the new isotope167W were observed in the reaction of 191 MeV36Ar with136Ba using a helium-jet and a fast tape-transport system. The identification is based on coincidences with tantalum X-rays and excitation function measurements. The measured half-life is 19.9(5) s. A decay scheme comprising 12 levels was constructed from γγ-coincidences. The β-decay is discussed within experimental and calculated level systematics. Alpha-rays with energy 4.55(2) MeV were assigned to167W.

The decay of the new isotope171Re

Irradiating LaF3-targets with36Ar, the decay of the new isotope171Re was observed for the first time and its half-life determined to be 15.2(4) s. Based on the measuredγ- and X-ray data, a decay scheme could be constructed.

The decay of the isotopes176Ir and177Ir

Abstract176,177Ir were produced by irradiation of141Pr with40Ar. β-delayed γ-rays of176,177Ir were observed for the first time. From γγ-coincidence data decay schemes could be constructed. A new half-life of177Ir was obtained yielding t1/2=30 (2) s. α-branching ratios of 3.1(6) % for176Ir and 0.06(1)% for177Ir were measured.