High-spin states in108Sn

High spin states in¹⁰⁸Sn have been investigated using the⁹²Mo(¹⁹F,p2nγ)¹⁰⁸Sn reaction. In-beam measurements ofγ-γ-coincidences,γ-ray excitation functions andγ-ray angular distributions were performed with Ge(Li)-detectors, one of which had a Nal Compton suppression shield. A level scheme for¹⁰⁸Sn has been constructed up to anI ^π=(14^?) state.     

Spectroscopy of highly excited states in29Si

Particleγ-ray coincidences have been measured in the²⁸Si (d,pγ) reaction at 6.5 and 7 MeV bombarding energy, in the²⁶Mg (α,nγ) reaction at 12, 14 and 15 MeV, and in the²⁷A1 (τ,pγ) reaction at 9 MeV. Theγ-decay has been observed for all bound states of²⁹Si and for 56 unbound states up to 12,960 KeV excitation energy. Particleγ-ray angular correlations were measured in the²⁸Si (d,pγ) reaction at 6.5 MeV and in the²⁶Mg (α,nγ) reaction at 12 MeV. Spin (-parity) assignments or restrictions were obtained for nearly all bound states and some high-spin states above the binding energy. The assignment of mirror levels in²⁹Si and²⁹P has been extended to 8.2 MeV excitation energy. The excitation energies of 41 positive-parity states are reproduced by shell model calculations. The possible existence of aK ^π=5/2⁺ band with prolate deformation is discussed.     

High-spin states in68Ga

The⁶⁸Ga nucleus has been studied via the reactions⁶⁵Cu(α, nγ)⁶⁸Ga atE _α=12–21 MeV and⁶⁶Zn(α, p nγ)⁶⁸Ga atE _α=25–40 MeV. The level scheme has been established by means of relative yield functions, electronic timing measurements, prompt and delayedγ-γ coincidences, angular distributions and directional orientation coÏncidences. Spins up to 11⁺ were assigned to levels up to 4 MeV excitation and the higher ones were interpreted by coupling a⁶⁷Ga core with a (v 1 g_9/2) neutron.     

Lifetime measurements in166Er

The lifetimes of five states in the ground band, from spin 6⁺ up to spin 14⁺, and of all even states in the gamma band up to spin 12⁺, have been measured in¹⁶⁶Er using the recoil distance method. The reduced electric quadrupole transition probabilities have been determined from the measured lifetimes using previously measured branching ratios, and the mixing between the ground band and theγ-band has been studied. The transitional electric quadrupole moments for the ground band and theγ-band have been deduced and are discussed.     

High-spin states in106Cd

Levels of¹⁰⁶Cd, populated by¹⁰⁴Pd(α, 2nγ)¹⁰⁶Cd have been studied measuring direct and delayedγ-ray spectra,γ-γ coincidences andγ-ray angular distributions. A decay level scheme is proposed including states up to 4659.8 keV. IntenseE2 transition cascades have been observed. The half-life of an isomeric level located at 4659.8 keV has been measured:T _1/2= 62±6ns. Nuclear Reactions ¹⁰⁴Pd(α, 2nγ),E _α=31MeV; measuredE _γ,I _γ,γ-γ coinc, σ(θ)T _1/2.¹⁰⁶Cd deduced levels,J, π, Enriched targets. Ge(Li) detectors.     

Constraints on the universe as a numerical simulation

The level scheme above the proton threshold in ²⁶Si is crucial for evaluating the ²⁵Al(p, γ)²⁶Si stellar reaction, which is important for understanding the astrophysical origin of the long-lived cosmic radioactivity ²⁶Al(T _1/2 = 7.17 × 10⁵ y) in the Galaxy. The excited states in ²⁶Si have been studied using an in-beam γ-ray spectroscopy technique with the ²⁴Mg(³He, nγ)²⁶Si reaction. γ-rays with energies up to 4.6 MeV emitted from excited states in ²⁶Si have been measured using large volume HPGe detectors. The spin-parity of one of the most important states reported recently at 5890.0keV has been assigned as 0⁺ by γ-γ angular correlation measurements in this work.     

Yrast and side bands in the odd-odd160, 162Tm nuclei

High-spin states in²⁰⁵Bi, populated in the²⁰⁵Tl(α, 4n) reaction with bombarding energies around 50 MeV have been studied usingγ-ray spectroscopic techniques. Spins and parities have been assigned on the basis of angular distribution andγ-ray linear polarization measurements. States with spins up to 39/2⁺ and excitation energies around 6 MeV have been identified. Calculations using the empirical shell model have been performed in order to assign configurations.     

Der zerfall des J121 (T 1/2=2,12 h)

I¹²¹ was produced by bombarding a target of enriched Te¹²² with deuterons of 25 MeV. Theγ rays associated with the decay of I¹²¹ have been investigated using a Ge(Li) detector and a Ge(Li)-NaI coincidence set up. 58γ transitions ranging from 212.5 to 1841.8 keV have been identified. A decay scheme for the I¹²¹→Te¹²¹ decay which accounts for 50 of the observedγ transitions is proposed.     

High-spin structure in154Er

High spin states in the nucleus¹⁵⁴Er have been reinvestigated using the¹²³Sb(³⁵Cl, 4n) reaction and a variety of spectroscopic techniques including excitation functions,γ-γ coincidences,γ angular distribution and linear polarization measurements. From the measured energies, relative intensities and transition multipolarities a new level scheme has been deduced up to an excitation energy of ～12 MeV and spin 36. An interpretation of the experimental results is given in terms of the deformed Woods-Saxon orbitals. Gigantic backbending (superdeformation) effect is studied theoretically within the cranking model.     

Nonlinear model-Boltzmann equations and exact solutions

The present paper is devoted to the subject of photonuclear reactions of the type (γ, p), (γ, n), (γ, np), (γ, nn), (γ, pp) as well as nucle on capture reactions as (p, γ) at intermediate photon energies. The theoretical part of this paper reviews and extends earlier calculations of the authors up t gamma energies of E_γ ≈ 400 MeV. The paper is not intended to give a review on different theoretical approaches which have been underta ken in the past. Instead, emphasis is put on the dynamical aspects of the photonuclear reactions in order to see which elementary processes govern the reactions at different photon energies. In view of the success of the present treatment up to E_γ ≈ 120 MeV photon energy, we tempt the predictive power of the model up to photon energies of E_γ ≈ 400 MeV for the reactions in ⁴He and ¹⁶O.     

Band structures in73Se

Excited states of⁷³Se have been investigated up to spin, 21/2 using techniques of in-beamγ-ray spectroscopy in connection with the⁷⁰Ge(α, n) reaction. Mean lifetimes of 12 levels have been determined applying Doppler-shift andγ-RF-methods. Five different bands have been identified that reflect a variety of different excitation modes. The decoupled 9/2⁺ band is likely to correspond to an oblate deformation while the 5/2⁺ band is interpreted as a strongly coupled prolate band built on the Nilsson configuration [422] 5/2⁺. The 3/2^? band is a strongly coupled band built on the [301] 3/2^} configuration.Nuclear reactions:⁷⁰Ge(α,n),E=14, 16, 18, 19, 20MeV; measuredE _γ,I _γ,σ(E _γ,θ),γγ-coin, linear polarization, DSA,γ(t).⁷⁵Se deduced levels,I, π, τ, δ(E2/M1), B(σλ). Enriched targets, Ge detectors.     

High-spin levels in137,139Ce and139,141Nd evidence for hole-core coupling

Excited states of the¹³⁷Ce,¹³⁹Ce,¹³⁹Nd and¹⁴¹Nd nuclei have been studied using the¹³⁸Ba(α, 5nγ)¹³⁷Ce,¹³⁸Ba(³He, 4nγ)¹³⁷Ce,¹³⁸Ba(α, 3nγ)¹³⁹Ce,¹⁴⁰Ce(α, 5nγ)¹³⁹Nd,¹⁴⁰Ce(³He,4nγ)¹³⁹Nd,¹⁴⁰Ce(α, 3nγ)¹⁴¹Nd and¹⁴²Ce(α, 5nγ)¹⁴¹Nd reactions. Singlesγ-ray spectra,γ —γ coincidence spectra, angular distributions and time distributions ofγ-rays with respect to beam pulses have been measured. Gamma transitions between excited states with spin values up to 21/2, 23/2 or 25/2 have been observed. Isomeric states with T_1/2=70 ns have been observed in¹³⁹Ce at 2631.5 keV (19/2) and in¹⁴¹Nd probably at 2952.0 keV (19/2). The level structure observed in the nuclei studied can be explained if the neutron-holes are coupled to the doubly even core excitations. The coupling of theh _11/2 neutron-hole with the 2⁺, 4⁺ and 3^? collective excitations are calculated in terms of the weak and intermediate coupling models. The intermediate coupling results seem to be in better agreement with the experimental data. The energies of theree-particle states, being the result of the coupling of theh _11/2 neutron-hole with the two-proton excitations in the core, are well reproduced in the calculations when empirical values of the two-body interaction matrix elements were used.     

Untersuchung der Kernphotoreaktionen12C(γ,n),12C(γ, 2n),39K(γ,n) und40Ca(γ,np) bis zur Mesonenschwelle

In order to obtain data on the photon absorption process between the giant resonance and the meson threshold the cross sections of the reactions¹²C(γ,n)¹¹C,¹²C(γ, 2n)¹⁰C,³⁹K(γ,n)³⁸K^g, and⁴⁰Ca(γ,np)³⁸K^g have been determined by the analysis of yield curves at the 140 MeV electron synchrotron of the PTB. Though the (γ,n) cross sections grow small with increasing photon energy they are different from zero up to energies of 60 MeV and above. The cross section of the reaction¹²C(γ, 2n) is extremely small; its highest value amounts to 0.15% of the highest value of the¹²C(γ,n) reaction. The measured⁴⁰Ca(γ,np) cross section is of the order predicted by the naive quasi-deuteron model. The integrated cross sections of the above reactions up to 140MeV are 85±7,0.90±0.10, 139±16, and 76±7MeVmb respectively.     

Gamma-ray spectroscopy of61Zn

The⁶¹Zn decay scheme and level properties have been investigated up to the 2,269.6 keV level by the⁵⁸Ni(α, n γ)⁶¹Zn reaction using enriched targets. Excitation functions,γ ray spectra andn-γ coincidence spectra have been measured as well as angular distributions and angular correlations in Litherland II geometry. Gamma ray energies, excited state spins andγ ray branching ratios have been determined.     

High-spin states in154Er

High-spin states in¹⁵⁴Er have been populated by bombarding¹⁴⁷Sm and¹⁴⁸Sm with¹²C particles. Excitation functions, lifetimes, angular distributions andγ-γ coincidences were measured. AT _1/2=35ns isomeric state atE _x～3 MeV has been found and is interpreted as a two-quasi-particle state with aligned angular momenta. A cascade of intense individual lines from states with spin up to at least 26 (excitation energy up to 8.543 MeV) was found to feed the isomeric state. The level sequence above this yrast trap exhibits an irregular pattern which cannot be easily interpreted in terms of collective modes.     

High-spin states in112Cd from the110Pd(α, 2n γ)-reaction

The decay scheme of¹¹²Cd has been studied by γ-ray spectroscopy with the¹¹⁰Pd(α, 2nγ) reaction. Spin and parity assignments were made on the basis of coincidence measurements, angular distributions and excitation functions. Twelve new energy levels were established. A vibrational-like positive-parity band up to spin 8⁺ and a negativeparity side band 5^?, (7^?), (9^?) were found. For the negative-parity states a (v_j, vh_11/2) configuration is suggested. Nuclear Reactions:¹¹⁰Pd(α,2nγ),E _α =15–22.5 MeV; measuredE _γ ,E _γ , (E,E _γ ),E _γ (θ),γ-γ- coincidence;¹¹²Cd deduced levels,J; enriched target.     

Levels in104Ru populated by the β−-decay of104Tc

Theβ ^? — andγ-activities of 18.4 min¹⁰⁴Tc have been studied with singles and coincidence measurements. Sources were prepared by chemical separation of technetium from the fission products of thermal-neutron-induced fission of²³⁵U. A revised level scheme of¹⁰⁴Ru up to an excitation energy of 4.26 MeV is proposed. Fromβ-γ coincidence measurements, aQ _β-value of 5.62±0.07 MeV has been obtained.     

Properties of excited levels in102Rh by the102Ru(p,nγ) reaction

The level scheme of¹⁰²Rh has been investigated by the¹⁰²Ru(p, nγ) reaction in the proton energy range 3.1 MeV≦E _p≦6 MeV. Excitation functions,γ-γ coincidences and pulsed beam measurements have been performed and a level scheme including 33 excited states up toE _x≈650 keV has been constructed. Theγ-branchings of several levels have also been measured. The lifetimes of 5 excited states have been determined with the centroid-shift method:τ _m(105.2 keV)=(1.3±0.3) ns,τ _m(123.7 keV)=(0.6±0.3) ns,τ _m(178.6 keV)=(1.5±0.3) ns,τ _m(208.7 keV)=(0.5±0.3) ns,τ _m(359.6 keV)=(0.8±0.4) ns. Upper limits have been placed for the lifetimes of 20 other levels.     

Electromagnetic transition rates and vibrational modes in34S

States in³⁴S up to 6 MeV excitation energy, populated by the reaction³¹P(α, pγ), have been investigated by Doppler shift and line shape analysis andpγ andγγ angular correlation measurements. The strengths of electromagnetic transitions between even parity levels are compared with theoretical predictions of the weak coupling unified model and the many-particle shell model. The experimental evidence for a weak coupling of the single particle motion to vibrational modes is discussed.     

Die Anregungszustände des79Br

Previous investigations of nuclear resonance fluorescence from⁷⁹Br have been improved by using a Ge-detector. In addition, energies and intensities of theγ transitions initiated by the decay of⁷⁹Kr have been remeasured. Coincidences between theγ transitions were investigated using two 40 ccm Ge-detectors. 14γ transitions unknown up to the present have been identified. A level scheme having 12 excited states is proposed. Unique assignments of spin and parity to the 7 lowest states became possible by the present and former experimental data.