L. I. Simonova

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.

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 levels in 187W

Abstract Levels in 187W have been studied up to 2.2 MeV with the (d, p) and (n, γ) reactions. The (d, p) studies were performed at deuteron energies of 24 and 28 MeV and at two angles of 30° and 50° by using the high resolution Q3D spectrograph in Munich. Primary and secondary γ-rays and γ-γ coincidences were studied with Ge detectors. The combination of these results with the previously known ones allows us to extend the existing level scheme and refine some of its structure assignments. Most of the low-lying states have been classified in terms of the Nilsson model with the extension of some vibrational degrees of freedom. The possibility for the coexistence of triaxial or oblate shapes in 187W is observed in the form of anti-aligned states with a bandhead of 9 2 − at 364 keV. The polarization effects towards the triaxial shape produced by the odd neutron in specific Nilsson orbitals have been studied. The calculated polarization energies for some γ-driving orbitals are comparable with the prolate-oblate energy difference which indicates the possibility of the stabilization of triaxial or oblate shapes in these states.

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.

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.

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.}

Intrinsic excitations in 192Ir

The structure of the odd‐odd 192Ir nucleus presents an interesting and challenging problem for both experimentalists and theorists. As a result of the common efforts of nine laboratories, it is possible, for the first time, to propose an extended scheme with 34 levels. The experiments included observation of γ‐ray transitions and of conversion electrons emitted after thermal and resonance neutron capture, of direct (d,p) and (d,t) neutron transfer reactions and of the angular distribution of γ‐rays from aligned 192Ir nuclei. The results are interpreted in the framework of the rotor‐plus‐particle and IBFFM models. The nuclear states appear to be strongly mixed. The complex and interesting ground‐state configuration is discussed.

Transitions in41K studied with the (n, n??) reaction

Singles gamma ray spectra of the41K(n, n′γ)41K reaction have been measured with fast reactor neutrons. The populated states and γ-ray intensities are compared with those of the40K(n, γ)41K reaction. About 91% of the observed gamma ray intensity was assigned to the decay of 35 states in41K. The energy and spin dependence of the gamma ray fluxes in both reactions are discussed.