M. Balodis

Nuclear levels in152Eu

The transitional nucleus152Eu has been studied using the (n, e), (n, γ), (nres,γ), (n, γγ), (d, p), (d, t) and (p, d) reactions. The experiments have been performed at nine different laboratories. A model independent level scheme was established including 95 levels below 510 keV and nearly 900 transitions by combination of low energy transitions and reaction data. More than 20 additional levels result from gamma rays and/or charged particle reactions. The level scheme is interpreted in terms of the Nilsson model indicating that152Eu is a deformed nucleus. Seven rotational bands and Nilsson configurations are established. An additional 27 rotational bands are tentatively or speculatively assugned. Gallagher-Moszkowski splittings are discussed. The neutron binding energy was determined as 6305.2±0.5 keV. The energy of the 9.3 h 0− isomer is 45.599 keV. The lifetimes of four levels were measured.Nuclear Reactions151Eu(n,γ),En=thermal and resonance; measuredEγ,Iγ,Ec.e.,Ic.e.,γγ Coinc.,γγΔt coinc.;151Eu(d, p),E=12MeV and 14MeV;153Eu(d, t),E=12MeV;153Eu(p, d),E =18MeV; deduced level scheme of152Eu,J, π, T1/2,cc, Nilsson configurations. Magnetic electron spectrometer, curved crystal spectrometer, Ge(Li) and Si(Li) detectors, magnetic spectrographs. Enriched targets.

Nuclear levels in 160Tb

Abstract The high energy γ-ray spectrum from thermal neutron capture in natural terbium has been studied over the energy range of 5200 to 6400 keV. Low energy γ-radiation of the same reaction has been observed from 20 to 1230 keV and conversion electrons from 6 to 160 keV. Low energy (n, γγ) coincidences have been measured. A value of 6375.1 ± 0.3 keV has been obtained for the neutron binding energy in 160Tb. The data, when combined with a previous 159Tb (d, p) study, allow a level scheme to be constructed. These levels are assigned to nine rotational bands built on two quasiparticle configurations. The decay of several other levels is discussed. In three cases we have observed both parallel and antiparallel coupled bands with K − = ¦Ω p −Ω n ¦ and K + = Ω p + Ω n , and found the Gallagher-Moszkowski rule to be valid. The energy splitting has been calculated using Nilsson wave functions and a δ-force. Two K = 1 bands with irregular level spacing have been observed.

The level scheme of 176Lu investigated by (n, γ) and (n, e) reactions

Abstract The excited levels of 176 Lu have been studied using the conversion electron and γ-spectra from slow neutron capture in 175 Lu measured with the β-spectrograph at Riga and with the diffraction spectrometer at Riso. The proposed level scheme contains the rotational bands with the following lowest levels E , I π K and Nilsson configurations: 126 keV , 1 − 0, p 7 2 + [404]− n 7 2 − [514] ; 198 keV , 1 + 1, p 7 2 + [404]− n 9 2 + [624]; 342 keV , 1 + 1, p 9 2 − [514]−n 7 2 − [514]; 390 keV , 1 − 1, p 7 2 + [404]− 5 2 − [512]; 638 keV , 4 + 4, p 1 2 − [541]+ n 7 2 − [514]; 641 keV , 1 − 1, p 5 2 + [402]−n 7 2 − [514]; 660 keV , 5 + 5, p 9 2 − [514]+ n 1 2 − [510]; 662 keV , 3 − 3, p 7 2 + [404]−n 1 2 − [510]; 726 keV , 4 − 4, p 1 2 + [411]+ n 7 2 − [514] . The bands with 0 keV, 7 − 7, p 7 2 + [404]+ n 7 2 − [514] and 404 keV, 8 + 8, p 7 2 + [404]+ n 9 2 + [624] , can be discussed only on the basis of earlier (d, p) and (d, d′) reaction data.

Levels in 154Eu populated by (n, γ) and (d, p) reactions

Abstract The structure of the doubly-odd nucleus 154 Eu was investigated using neutron capture and (d, p) reactions on 153 Eu. The low-energy γ-ray and conversion electron spectra from thermal neutron capture, as well as the γ-ray spectrum for primary energies up to 6.5 MeV, were measured with precision instruments at the Institut Laue-Langevin, Grenoble. The multipolarities were determined for most of the detected low-energy transitions. The (n res , γ high ) spectrum measurements with 2 keV, 2 eV and 3 eV neutrons were performed at Brookhaven National Laboratory for primary transitions leading to the 0–600 keV excitation energies. The 153 Eu(d, p) 154 Eu reaction was measured with the Q3D spectrograph at TU Munich. A level scheme below 600 keV excitation energy comprising 99 levels was deduced and the parities and most probable spin values were determined from the experimental data. The low-lying levels were interpreted as due to the two-particle Nilsson configurations, taking into account the proton orbits 5 2 + [413], 5 2 − [532], 3 2 + [411] , and the neutron orbits 11 2 − [505], 3 2 + [651], 3 2 − [521], 3 2 − [532], 5 2 + [642], 3 2 + [402], 5 2 − [523], 1 2 + [400], 1 2 − [530] . The 145.3 (± 0.3) keV level observed in the (d, p) reaction can be identified with the isomeric level with T 1 2 = 46 min . The neutron separation energy for 154 Eu was determined to be 6442.0 ± 0.3 keV.

Nuclear structure of 183W studied in (n, γ), (n, n′γ) and (d, p) reactions

Abstract The nucleus 183 W was studied with ( n , γ), ( n , γγ) and ( n , n ′ γ ) reactions at the Nuclear Research Center Reactor in Riga and with the ( d , p ) reaction measured with the Q3D spectrograph at the Munich Tandem Accelerator. The 183 W γ-transition data from the ( n , γ) reaction were obtained in the energy range from 90 to 6200 keV and from the ( n , n ′ γ ) reaction in the energy range from 40 to 2080 keV. The new data allowed to obtain much more accurately the energies and depopulation of excited levels, and to extend the level scheme up to about 1.7 MeV. The one-quasiparticle states below 1.6 MeV were interpreted as belonging to the Nilsson configurations 1 2 − [510] , 1 2 − [501] , 1 2 − [521] , 3 2 − [512] , 3 2 − [501] , 3 2 − [521] , 3 2 + [642] , 3 2 + [651] , 5 2 + [642] , 5 2 − [512] , 7 2 − [503] , 7 2 − [514] , 9 2 − [505] , 9 2 + [624] , 11 2 + [615] and to the βγ-vibrational band. Structure calculations in terms of the quasiparticle-phonon and quasiparticle-rotation-vibration models were performed.

Level structure of the odd-odd nucleus 156Eu

Abstract The reaction chain 153 Eu(n, γ) 154 Eu(n, γ) 155 Eu(n, γ) 156 Eu was studied using 153 Eu targets. The γ-ray and internal conversion electron spectra were measured with high resolution spectrometers. Using several subsequent measurement series, as well as the radiation spectra from the reaction-decay chain 154 Sm(n, γ) 155 Sm 155 Eu(n, γ) 156 Eu, we assigned 95 transitions to 156 Eu, and 70 multipolarities were determined for them. 31 levels with spin values from 0 to 5 were found up to 515 keV. These levels are assigned to 13 rotational bands interpreted using proton orbits p 5 2 + [413]↓, p 5 2 − [532]↑, p 3 2 + [411]↑ and neutron orbits n 5 2 + [642]↑, n 3 2 − [521]↑, n 5 2 − [523]↓, n 11 2 − [505]↑ . Comparison with the decay of 156 Sm to 156 Eu indicates a 0.7% β-branch to the 1 − level at 266.95 keV, and log ƒt = 7.1 . The 434.230(2) keV energy is proposed for the level 448 ± 15 keV , 3 − , p 5 2 + [413]↓− n 11 2 − [505]↑ , earlier known from the 154 Eu(t, p) measurements. Model calculations are in agreement with the Gallagher-Moszkowski rule for four doublets Ω p ±Ω n . The calculated mixing amplitudes explain origin of some two-particle transitions. Comparatively intense E1 transitions between levels of bands with ΔK = 0 and opposite parities allow to propose existence of octupole deformation in 156 Eu which results in observation of parity doublets. It can be estimated that the 156 Eu level scheme is complete up to about 240 keV excitation energy for all spin values.

Excited levels of Ho166

Abstract The internal conversion electron spectrum in the reaction Ho165(n, γ)Ho166 has been measured with a β-spectrograph. Within the energy interval 40–300 keV, energies and intensities of conversion electron lines have been determined. The scheme of low-energy levels in Ho166 is discussed. The characteristics 3−, 4− are proposed for the levels at 170.6 keV and 240.1 keV instead of assignments existing in the literature.

Transfer and neutron capture reactions to 194Ir as a test of Uν(6/12)⊗Uπ(6/4) supersymmetry

The structure of 194 Ir is investigated via (n, y), (n, e - ), (d, p), and (d, a) spectroscopy. The use of different methods leads to an almost complete level scheme up to high excitation energies including γ-decay and spin-parity assignments. A reanalysis of the formerly published (n, y) data was triggered by our new (d, p) and (d, a) transfer reactions. The experimental level scheme is compared to predictions using extended supersymmetry. Herein, the classification of states was done according to quantum numbers, excitation energies, and (d, a) transfer strengths. A one-to-one correspondence in excitation energies was obtained for the 23 lowest lying theoretical states with similar structures for the experimental and calculated level schemes. The two-nucleon transfer strengths show remarkable agreement. A Nilsson classification is discussed as well.

Level scheme of 194Ir

Abstract Levels of 194 Ir were studied using neutron capture and ( d , p ) reaction spectroscopy. A pair spectrometer was used to measure the high-energy γ-ray spectrum from thermal-neutron capture in an enriched 193 Ir target over the energy range 4640–6100 keV. From the same reaction, low-energy γ-radiation was studied using curved-crystal spectrometers, and conversion electrons were observed with magnetic spectrometers. Prompt and delayed γγ-coincidences were measured using semiconductor and scintillation detectors. Averaged resonance capture measurements were performed with 2 keV and 24 keV neutrons for primary transitions leading to excitation energies from 0 to 580 keV. Using 22 MeV deuterons, the 193 Ir( d , p ) high resolution spectra were observed with a magnetic spectrograph. The deduced nuclear level scheme of 194 Ir includes 38 levels connected by 184 transitions. Unambiguous spins and parities were determined for 25 levels. The rotor-plus-particle model was used for the interpretation of the level scheme assuming a strong mixing for Nilsson configurations having identical parities and K quantum numbers. IBFFM model calculations were performed and the obtained results were compared with the experimental level scheme.

Nuclear structure of {sup 170}Tm from neutron-capture and ({ital d},{ital p})-reaction measurements

We have made experimental measurements in {sup 170}Tm of the following: secondary {gamma} rays, conversion electrons, and {gamma}-{gamma} coincidences from thermal neutron capture in {sup 169}Tm, primary {gamma} rays from average resonance capture with 2-keV and 24-keV neutron beams, and proton spectra from the ({ital d},{ital p}) reaction on {sup 169}Tm. From these data and those of previous investigations, we have identified more than 130 excited levels in {sup 170}Tm below 1550 keV. Of these, 62 (with connecting transitions) are placed in 18 rotational bands with assigned Nilsson configurations. These results are in good agreement with a semiempirical modeling of {sup 170}Tm level structure. Values for seven Gallagher-Moszkowski splittings and four Newby shifts have been obtained. These matrix elements show remarkably good agreement with calculation. Among the observed {ital K}{sup {pi}}=1{sup {minus}} and 2{sup {minus}} rotational bands, configuration mixing appears to play a significant role. {copyright} {ital 1996 The American Physical Society.}