V.V. Kuznetsov

The decay of 152Tb

Abstract The conversion electron spectrum, electron-gamma and β + -gamma coincidence spectra are investigated, and the gamma-ray spectrum is studied in two Ge(Li) semiconductor spectrometers. A decay scheme 152 Tb → 152 Gd is suggested, including many new levels among which two 0 + states at 1484.0 and 2720.7 keV. Relative intensities at 0.2 : 0.3 : 1 are found for positon branches from 152 Tb to the 615.6 keV (0 + ), 344.4 keV (2 + ) and to the ground state of 152 Gd. Spin 1 − is ascribed to the ground state of 152 Tb. Spin assignments are being made for the following excited levels: 755.6 keV 4 + , 1109.8 keV 2 + , 1123.8 keV 3 − , 1606.1 keV 2 + , 1643.9 keV 1 − , 1862.3 keV 2 + and 1942.5 keV 2 + .

Investigation of the spectra of conversion electrons and positons of the Nd fraction new isotope Nd137

Abstract Targets of Ta and Er were irradiated with a proton beam from the Dubna synchrocyclotron. The conversion electrons and the positons of the Nd spallation fraction were studied by a beta-spectrometer. A new activity with a half-life of 55±1.5 min was observed. It is established that this activity is due to the decay of Nd 137 to Pr 137 . A decay scheme is proposed.

Excited states of the doubly odd deformed nucleus 160Tm

Abstract The decay of 4.8 min 160 Yb has been investigated by means of Ge(Li) detectors, toroidal and magnetic-lens β-spectrometers and scintillation counters. The singles spectra of γ-rays and conversion electrons as well as prompt and delayed γ-γ and γ-ce coincidences have been measured. The 160 Tm level scheme is proposed including 94.5% of the total γ-ray intensity observed in the 160 Yb decay. The lifetimes of the 42.02, 174.40 and 215.78 keV states have been determined to be 1.6±0.3, 17±1 and 0.65±0.15 ns, respectively. From the analysis of the experimental data, the quantum characteristics of 160 Tm levels are proposed. Experimental γ-ray transition probabilities are compared with Weisskopf and Nilsson estimates, the latter also taking into account pairing correlations.

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 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.

155Gd levels excited in the decay of155Tb

Conversion electron spectra, gamma rays, and e-γ and γ-γ coincidences in the decay of155Tb were investigated. The conversion electron spectra were measured with a toroidal six-gap beta spectrometer and a two-fold double-focusing π √2 beta spectrometer. The gamma rays were measured by means of Ge(Li) detectors. The e-γ-coincidence spectra were investigated by means of the six-gap beta spectrometer and a NaI(Tl)-gamma spectrometer. The γ-γ-coincidences were studied by the method of two-dimensional analysis with the use of two coaxial Ge(Li) detectors.A number of transitions was found in155Tb decay which were not observed up to now. A more complete scheme of the decay155Tb →155Gd is proposed.Conclusions were reached on the multipolarity of most transitions and possible spin and parity values were determined for the155Gd levels.The populations of the excited levels in155Gd ware determined and the lgft values were calculated.A comparison of the results obtained with the calculations by Solovev et al. based on the superfluid model of the nucleus enables one to assign the structure to the 592·6 keV state as follows: [521]↑−0·7%, [521]↑+Q1(20)−99% and to interpret the 559·9 keV level as a mixed state of the type [521]↺−42%, [521]↑+Q1(22)−37%, [523]↺+Q1(22)−16%.

Levels in 161Tm excited in the decay of 4.2 min 161Yb

Abstract The decay of 161 Yb ( T 1 2 = 4.2 min ) has been investigated with Ge(Li) and Si(Li) detectors and a toroidal β-spectrometer. Isobarically separated samples produced by the YASNAPP facility at Dubna Institute were used. The singles γ-ray spectrum, the conversion electron spectrum, γ-γ-τ and e-γ coincidences have been measured. In all, 67 γ-ray transitions have been observed. A decay scheme for 161 Yb is proposed involving 12 excited states in 161 Tm. The 7 2 + [404], 7 2 − [523] and 5 2 + [402] levels have been identified. The interpretation of the high-lying levels is discussed. The Q -value of 161 Yb decay has been determined to be 3850 ± 250 keV. The A -dependence of the energies of the one-quasiparticle states in odd- A Tm isotopes is demonstrated.