H. Strusny

Decay of 167Yb (18min) to 167Tm

Abstract The level scheme of the deformed nucleus 167Tm has been investigated in the decay of 167Yb using germanium detectors and a magnetic β-spectrograph. The conversion electron spectrum, single γ-ray spectra and prompt and delayed γ-γ coincidences were measured. A decay scheme is proposed involving 25 excited states in 167Tm and approximately 60 of the more than 100 new transitions. In the low-energy region the first members of the rotational bands 1 2 + [411], 1 2 − [541], 7 2 + [404], 7 2 − [523] and 3 2 + [411] could be identif interpretation of the high-lying levels are discussed on the basis of microscopic theory.

Investigation of i132 excitations in 197Hg and 191Pt

Abstract The level schemes of the odd-neutron nuclei 197 Hg and 191 Pt have been studied using in-beam spectroscopic methods. Energies, intensities, angular distributions and coincidences of the γ-rays following (α, 2n) reactions were measured. Also conversion electrons and delayed γ-ray spectra were recorded. Most of the levels in both nuclei are de-populated via the 13 2 + isomers. Besides the yrast states, several additional states with spin values between 13 2 and 21 2 were identified. The negative parity of a side band in 197 Hg starting with an f = 21 2 state was proved by the conversion electron measurement. The families of positive-parity states were compared with model calculations where the core was described as rigid triaxial rotor or anharmonic vibrator. For 197 Hg both models give similarly good results for the energy spectrum and the branching ratios of electromagnetic transitions. Several negative-parity states found in 197 Hg are compared with the predictions of a pairing-plus-quadrupole model.

Decay of 161Er to 161Ho

The level scheme of the deformed odd-proton nucleus 161Ho was investigated in the electron-capture decay of 161Er using germanium detectors, a magnetic β-spectrograph and two π√2 double-focussing β-spectrometers. In addition to the measurements of singles γ-ray and conversion-electron spectra extensive γ-γ coincidence measurements were performed. A decay scheme is proposed involving 37 excited states in 161Ho. In the low-energy region the first members of the rotational bands 72-[523], 12+[411], 72+[404], 32 +[4411], 12−[541], 52+[413] and52−[532] were identified. Furthermore, the first two members of the γ-vibrational band K0-2M built on the ground state and an additional band with the probable quantum characteristic Kπ = 52+ (band head at 446.9 keV) have been found. Possible interpretations of the high-lying levels are discussed on the basis of current models.

Levels in 163Tm excited by the decay of 11.4 min 163Yb

Abstract The decay of 163 Yb (T 1 2 = 11.4 min ) has been investigated with Ge(Li),Si(Li) and NaI(Tl) detectors, a toroidal β-spectrometer and magnetic β-spectrographs by using isobarically separated samples produced by the YASNAPP facility at Dubna. The singles γ-ray spectrum, the conversion electron spectrum, prompt and delayed γ-γ coincidences and β + - γ coincidences have been measured. In all, 110 new γ-ray transitions have been observed. A decay scheme for 163 Yb is proposed involving thirty excited states in 163 Tm. The first members of the rotational bands 1 2 + [411], 7 2 + [404], 1 2 − [541], 3 2 + [411] and 7 2 − [523] have been identified. Possibilities of interpretation for the high-lying levels are discussed. The Q -value of 163 Yb has been determined to be 3370±100 keV.

The decay chain162Yb (19·0 min) →162Tm (21·8 min) →162Er and the decay of160Tm (9·2 min) TO160Er

The decay of162Yb,162Tm and160Tm has been investigated with Ge(Li) and Si(Li) detectors using isotopically separated samples produced by the YASNAPP facility at Dubna. The singles γ-ray spectrum, β-γ and γ-γ coincidences were measured. Strong ytterbium and thulium activities were used for conversion electron measurements with high resolution magnetic β-spectrographs. 3, 134 and 39 new γ-rays were attributed to the decays of162Yb,162Tm and160Tm, respectively. Decay schemes of these isotopes are proposed. Three and 12 new levels were found in162Er and160Er, respectively. TheQ-values of162Yb,162Tm and160Tm were determined to be ≦2·2, MeV, 4·6±0·3 MeV and 4·9±0·5 MeV, respectively.

High-spin states of the doubly odd nucleus 178Ta

The properties of levels in 178Ta have been investigated via the reactions 176Lu(α, 2n)178Ta, 178Hf(d, 2n)178Ta and 178Hf(p, n)178Ta. Energies, intensities, angular distributions, prompt and delayed coincidence relations of γ-ray transitions, lifetimes of isomeric levels as well as conversion electron spectra have been measured. The high-spin states observed have been assigned to rotational bands built on proton-neutron two-quasiparticle excitations with Kπ = 6−, 7−, (8)+ and 9−, respectively. A high-spin isomer with a half-life of T12 = 60 ms has been found at 1470.6 keV and assigned as a 15− four-quasiparticle state. Nilsson configurations are proposed for most of the levels.

The decay of 159Tm (9.0 min) to 159Er

The decay of 159Tm (T12 = 9.0±0.4min) has been investigated with Ge(Li) andSi(Li) detectors, B-spectrographs and a toroidal spectrometer using isotopically separated samples produced by the YASNAPP facility at Dubna. The singles γ-ray spectrum, the conversion electron spectrum, the positron spectrum, prompt and delayed γ-γ coincidences were measured. Using strong thulium activities, conversion electrons were also measured with high resolution b-spectrographs. In the 159Tm decay 81 new γ-ray transitions were observed. A decay scheme of 159Tm is proposed involving 12 excited states in 159Er. The first members of the rotational bands 32−[521], 52−[523], 32+[402 + 651], 112−505 and 72−[514] and the 52, 72 and 92 states of a strongly perturbed positive parity band were identified. The Q-value of 159Tm was determined to be 3.4±0.3 MeV.