Evidence for width correlation in the173Yb(n, γ)174Yb reaction

The¹⁷³Yb(n, γ)¹⁷⁴Yb reaction was measured at the Pulsed Fast Reactor. Intensities of 9 primary transitions toJ ^π =1⁺, 2 or 3⁺ levels below 1960 keV for 9 resonances withJ ^π =2_? were examined. Statistically significant correlation between reduced neutron widths and partial radiation widths has been observed.     

Scattering and resonance properties of the interaction of slow neutrons with the isotopes of silicon and sulfur

In¹¹⁷Te,¹¹⁹Te and¹²¹Te isomeric states withJ ^π=5/2⁺, 5/2⁺ and 7/2⁺ and half-lives of 19.1(9)ns, 2.2(2) ns and 86(6) ns, respectively, have been identified at low excitation energies using (α, 2n) reactions on enriched^115–119Sn targets. Positive parityΔJ=1 bands built on these isomeric states have been observed up to 17/2⁺. The states are interpreted as members of rotational bands built on deformation driving 5/2⁺ [402] and 7/2⁺ [404] Nilsson orbitals which overcome theN=64 subshell gap. The irregular level spacings and electromagnetic properties of the bands are well explained in Coriolis calculations. The moment of inertia parameter as function of collective angular momentum has been derived from the doubly even Te cores. The hindrance of the band head deexcitation may be caused by shape fluctuations of these transitional nuclei.     

Search for collectiveM3 excitations to low lying states in164Dy

We report on the search for mixed symmetricJ ^π=3⁺ states in the strongly deformed nucleus¹⁶⁴Dy and present an upper limit for theM3 transition strength. From the excitation of the symmetric 3⁺ state at 828 keV we deduce theF-scalar magnetic octupoleg-factor.     

Electroexcitation of magnetic dipole and other modes in46Ti and48Ti

With high-resolution inelastic electron scattering measurements on⁴⁶Ti and⁴⁸Ti the excitation mechanism of the transition into low lying J^π=1⁺ states is investigated. The experimental evidence of considerable contribution of the orbital part of theM1 operator to the total transition strength is given by a model dependent analysis of form factors. The possibility of physical relationship to low lying J^π=1⁺ states in the rare earth nuclei is discussed in various models. MoreoverE2 form factors and good candidates forM3 form factors are presented.     

Richtungskorrelationsuntersuchungen an den γ-Kaskaden des131Cs

The¹³¹Cs decay has been studied by angular correlation measurements of the (404-216), (832-216), and (247-373) keV γ-cascades using NaJ(Tl)-detectors in connection with a two parameter multi-channel analyzer. Unique spin assignments are obtained for the 216 (Jπ=3/2⁺) and 373 (Jπ=3/2⁺) keV levels. A previously discussed value ofJπ=5/2⁺ for the 1048 keV level is ruled out. The multipole character of the 404 keV transition is found to beE2 with less than 2%M1.     

Nuclearg-factors of theJ π=21/2+isomer in112In and theJ π=6+ 112Sn

Theg-factor of theJ ^π=21/2⁺ isomeric state in¹¹¹In (T _1/2=13.3 ns) and of theJ ^π=6⁺ isomeric state in¹¹²Sn (T _1/2=13.7 ns) were measured using the spin rotation method. The result obtained for theJ ^π=21/2⁺ level in¹¹¹In,g=+0.47 (2), indicates that this state has an almost pure ((πg _9/2)^?1 νg _7/2 νd _5/2) shell model configuration. The experimental valueg=+0.04 (3) for theJ ^π=6⁺ isomer in¹¹²Sn agrees with the theoretical value calculated within the frame of the BCS model.     

Der Zerfall des 1,5 min-Isomers Co54m

Co^54m (T _1/2=1.43 min) was produced in iron-foils by irradiation with_dE=19 MeV deuterons. The gamma ray spectrum was investigated using a NaJ(Tl) scintillation spectrometer, a coincidence circuit and a Ge(Li)-counter. There were observed three gamma rays having the following energies and intensities per Co_54m decay: 411 keV (0.97±0.07), 1130keV (0.98±0.05), 1407 keV (1.00±0.05). The directional correlation between the pairs of gamma rays were determined. These results correspond to spin and parityJ _π=2⁺ for the 1407 keV,J _π=4⁺ for the 2537 keV, andJ _π=6⁺ for the 2948 keV energy level of Fe⁵⁴. The last-mentioned level was not excited in previous scattering experiments. Our results are compatible withE=210keV andJ _π=6⁺ or 7⁺ of the isomeric state of Co^54m .     

New nuclides: Neptunium-243 and neptunium-244

We have observedγ-rays following the β^?-decay of²⁴³Np and²⁴⁴Np after chemical isolation of neptunium isotopes from the products of the reaction of 835 MeV¹³⁶Xe with²⁴⁴Pu. The ground-state of 1.85-min²⁴³Np hasJ=5/2. The decay of 2.29-min²⁴⁴Np (probableJ ^π=7^?) populates high-spin members of the ground state rotational band in²⁴⁴Pu.     

Half-life and configuration of the 1/2+ intruder state in203Bi

The decay properties of theJ ^π=1/2⁺,E _exc=1,098 keV state in²⁰³Bi were studied. The state was populated via the²⁰⁴Pb(p, 2n) reaction and the activity was studied with the ion guide isotope separator on-line system IGISOL. The half-life of the 1/2⁺ state was measured to beT _1/2=303 ±5 ms. From this value the partial half-lives of the three depopulating branches 1/2⁺ →7/2^? (E3), 1/2⁺→5/2^? (E3 +M2) and 1/2⁺→9/2 _g.s. ^? (M4) were deduced. Since all the transitions are configuration forbidden in first order, a detailed study of second-order shell-model configuration mixing could be performed.     

A microscopic investigation of gR and band cut-off effects

An in-beam study of excited states in¹⁴⁰Ce revealed 16 new levels of positive and negative parity on top of the 6⁺ isomer. The excitation energies of these states are well reproduced by diagonalizing the same Hamiltonian in two model spaces, aπ=+1 shell-model basis and aπ=?1 particle-core coupling basis.     

High-spin states in26Mg

Theγ-decays of levels in²⁶Mg have been investigated up to 12.5 MeV excitation energy by proton-γ-ray coincidence measurements in the²³Na(α, pγ) reaction at 14.2 and 16 MeV bombarding energy. Lifetime-measurements, made with the Doppler-shift attenuation method, and proton-γ-ray angular-correlation measurements were performed at E_α=14.2 MeV. Many high-spin states were observed, among them levels at 6,978 (5⁺), 7,283(4^?), 7,395(5⁺), 7,953(5^?), 8,202(6⁺), 8,472(6⁺), 9,065(5), 9,112(6⁺), 9,169(6^?), 9,383 (6⁺), 9,542(5), 9,829(7⁺), 9,989(6⁺) and 12,479(8⁺, 7^?) keV excitation energy. The spectrum of positive-parity states and their electromagnetic properties are reproduced with good accuracy by shell-model calculations which employ a unifieds-d shell Hamiltonian and the unrestricted configuration space of the 0d _5/2 1s _1/2 0d _3/2 shell. Members of five inferred rotational bands, withK ^π=0⁺, 2⁺, 3⁺, 0⁺ and 3^? have been observed up to at leastI=6. TheK ^π=2⁺ band shows strong anomalies of excitation energies andE2 transition rates near theI=6 state. The static intrinsic quadrupole moments calculated from the shell model wave functions indicate transitions from prolate to oblate deformation within theK ^π=2⁺ band and also the ground state band. The lowest lyingI ^π=4⁺ state appears to be “spherical” and cannot be associated with a rotational band.     

Internal electron-positron pair production from electric monopole transitions

The yield curve of the reaction⁵⁶Fe(p,γ)⁵⁷Co has been measured over the energy rangeE _p =1,300–1,900 keV and the decay of nine resonances has been investigated. For twelve of the resonances the strengths have been determined. The angular distributions of the gamma rays have been recorded for resonances atE _p =1,599, 1,623, 1,643 and 1,649 keV, giving spin-parity assignmentsJ ^π=3/2^? for all four resonances. The resonances atE _p =1,623, 1,643 and 1,649 keV have been identified as the split analogue resonances of the 367 (J ^π=3/2^?) states in⁵⁷Fe. TheM1 transition strengths to the corresponding antianalogue states have been measured and compared with theoretical predictions.     

Messung der zirkularen polarisation von γ-strahlung nach einfang polarisierter thermischer neutronen in kernen

A 70% polarized thermal neutron flux of 6 · 10⁶ s^? was obtained by total reflexion of a 1 m long Co-Fe mirror. Naturel targets of Al, Co, Mo and Sm where exposed to this beam. The measurement of the circular polarization of high energy captureγ-rays yielded some information about nuclear properties: For the transition from the compound state to the ground state in²⁸Al we derived theE2/M1 mixing ratioδ=?2.0 _+1.0 ^?0.5 . In⁹⁶Mo we obtained for the spin of the 2.25 MeV levelJ ^π=2^? or 3^?. If in agreement with theory the spin for this level isJ ^π=3^? the compound state for this decay hasJ ^π=2⁺ for over 50% of the transitions. In accordence with a previous measurement we found for the spins of the doublet in⁶⁰Co at 0.278 and 0.288 MeVJ ^π=3⁺ or 4⁺. For¹⁵⁰Sm we determined the overall circularγ-polarization. The measurement is in agreement with the statistical nuclear model yielding for the compound stateJ ^π=4^?. We confirmed the earlier spin assignementJ ^π=4⁺ for the 0.777 MeV level of¹⁵⁰Sm.     

Investigation of high spin states in23Na and23Mg and the12C+12C resonance atE c.m.=19.3 MeV

The resonance in the¹²C+¹²C system atE _c.m.=19.3 MeV has been studied in the neutron and proton decay channels. From(p, γ), (n, p) and (n, γ) coincidence measurements high spin states could be localized inA=23 nuclei, in²³Mg up to possibly 21/2⁺. These states were resonantly populated. The present data favorJ ^π=17/2⁺ for the 9.61 MeV state in²³Mg and therefore also for the probable parent state at 9.81 MeV in²³Na. AJ ^π=12⁺ assignment to the resonance is supported and evidence was found that the resonant excitation of the lowest 15/2⁺ and 17/2⁺ states in mass 23 nuclei is caused by a change of the intrinsic structure of the Yrast levels aroundJ ^π=15/2⁺ towards larger deformation.     

Colour-exotic constitutent quarks and hadron spectroscopy

Hypothetical colour-exotic constituent (or dressed) quarks are discussed. It is shown that the data on the excited baryons withJ ^P =1/2⁺, 3/2⁺ and excited mesons withJ ^P =0^?, 1^? are in a reasonable agreement with the hypothesis of the existence of colour-exotic quark in the colour state \(\bar 6\) .     

Triple differential cross section for angle,atomic number and energy (or angular momentum transfer) calculated for the 280MeV40Ar+58Ni (or 365MeV63Cu+197Au) system in a simple model

Highly excited levels of³³S populated by α-particle capture in²⁹Si have been investigated forE _α=1.962 MeV to 4.287 MeV. Excitation curves measured with Ge(Li) and BF₃ detectors are reported. More than fifty resonances can be identified with levels in³³S. (α, γ) angular distributions measured on five strong resonances have yieldedJ ^π values 1/2+, 3/2 +, 5/2?, 5/2?, 5/2? and 3/2+ respectively, for theE _x =10.054, 10.466, 10.523, 10.721, 10.758 and 10.776 MeV levels in³³S. Elastic scattering experiments have been performed and theJ ^π assignments are found to be consistent with thel-values inferred from the elastic scattering data. Decay schemes from the above³³S levels have been proposed. A new level at 9.245 MeV is also suggested and theJ ^π values for the 4.425 and 2.87 MeV states are shown to be consistent with 7/2+ and 3/2+ assignment, respectively. Nuclear Reactions²⁹Si(α, γ) and²⁹Si(α, α),E _α=1.962-4.287 MeV. Measured relative σ(E). DeducedJ ^π andE _γ of³³S levels. New³³S level atE _x =9.245 MeV. Enriched targets.     

Description of charge-exchange resonances in deformed nuclei

The (p, n) and (n, p) transition strength functions with excitation of the GT resonance, other 1⁺ states, spin-dipole with λ^π=0^- andE1 charge-exchange resonances in deformed nuclei in the regions 156≦A≦168 and 236≦A≦240 are calculated in the RPA. It is shown that the GT resonance has a maximum at 18–20 MeV, and in the region of 5–6 MeV around maximum (60–70)% of strength is concentrated. The spindipole resonance with λ^π=0^-, 1^- and 2^? strength is distributed within 14–33 MeV and theE1 strength within 25–29 MeV. The latter is splitted withΔE equal to 0.6–2 MeV into two peaks withI ^π I=1^-0 and 1^?1. In the region of 4–7 MeV around maximum 73–77% ofE1 strength is concentrated. The total (n,p) transition strength is 10–200 times as small as the total (p, n) transition strength.     

Study of5Li around 20 MeV excitation energy by a radiative capture reaction

The nucleus⁵Li has been investigated within an excitation range of 17.8 – 21.1 MeV by measuring γ-rays from the reaction D(τ, γ _o)⁵Li. In this range, excitation functions and angular distributions have been taken. The excitation functions exhibit broad maxima at 20 MeV which indicate, in agreement with other results, a level or a group of levels. Assuming that there is only one resonance, its properties are discussed. On the basis of the existing and the new experimental results, aJ ^π=1/2⁺ assignment is proposed besides the former resultJ ^π=(3/2, 5/2)⁺.     

Electroexcitation of isovector magnetic dipole and quadrupole transitions in 18O and their relation to radiative pion capture

In a high-resolution ¹⁸O(e, e′) experiment sharp states at E_X=16.38±0.01 MeV (J^π=2^?, ground state analogue of and at E_X=18.86±0.01 MeV (J^π=1⁺) and clustering of strength (possibly with J^π=1^?, 2^?) at E_X≈23.7 MeV have been observed and compared to theoretical predictions. The transition strengths for the narrow states are B(M2) ↑ = 58± 8 μ_K² fm² and B(M1) ↑ = 0.28± 0.04 μ_K², respectively. These results agree qualitatively with the resu lts from the analogous ¹⁸O(π^?, γ)¹⁸N reaction.