H. Salewski

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.

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.

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.

The decay of the isotopes179Ir and180Ir

Abstract179,180Ir were produced by irradiation of148Nd with36Ar. For179Ir, β-delayed γ-rays were observed for the first time and a decay scheme was constructed. For180Ir, the decay-scheme could be extended.

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.

Observation of a new ?-ray emitter:168W

Alpha-decay of168W was identified in136Ba(36Ar, 4n) and141Pr(32S, p4n) reactions. The α-ray energy was measured to be 4399 (12) keV. Using the intensity ratio of the simultaneously detected α-and 178.5 keV γ-rays, Iα/Iγ=4.1(6)·10−5 the α-branching is discussed.