Search

It was recently demonstrated that the empirical linear correlation of ${E(4}_{1}^{+})$ with ${E(2}_{1}^{+})$ is reproduced by the interacting boson model 1 (IBA-1) if a constant value for the coefficient $\ensuremath{\kappa}$ of the Q$\ensuremath{\cdot}$Q term is used. This constancy motivates the present investigation of whether it is possible to find sets of IBA-1 parameters, with fixed $\ensuremath{\kappa}$, that reproduce the data for a more general set of observables and a wide range of nuclei. A consistent procedure, based on contour plots of key observables, was used to extract $\ensuremath{\epsilon}$ and $\ensuremath{\chi}$ values for 145 nuclei spanning the $Z$ = 50--82 shell, which give reasonable overall agreement with the data with smoothly varying parameters. The constant $\ensuremath{\kappa}$ constraint sometimes leads to parameter values different than normal: finite $\ensuremath{\epsilon}$ values $(\ensuremath{\sim}$ 0.1 MeV) even for rotational nuclei and large $\ensuremath{\chi}$ values for transitional and vibrational nuclei that even increase towards the vibrational region. Finally, a systematic correlation of $\ensuremath{\epsilon}$ values with ${E(2}_{1}^{+})$ was found.

Two techniques for determining B(E2:01+ → 21+) values using low-energy Coulomb excitation of Radioactive Nuclear Beams in inverse kinematics are presented. One method, applicable if the lifetime of the excited state is ∼1 ns, uses a linear array of NaI(Tl) detectors to measure the decay curve, and thus the 21+ state lifetime, for Coulomb excited radioactive beam nuclei as they decay in flight downstream from a carbon excitation target. In the second method, useful when lifetimes are short

The low energy octupole states in {sup 134}Ba were examined using the inelastic scattering of 22 MeV protons. Strong fragmentation of the low energy octupole strength, which was observed in {sup 196,198}Pt and was identified as a signature of the O(6) dynamical symmetry limit of the interacting boson approximation (IBA), does {ital not} occur in {sup 134}Ba, which has been proposed to have O(6) structure. The model calculations demonstrate that there is, in fact, little difference in the structure of the low-lying positive parity levels between certain nuclei in a U(5){r_arrow}SU(3) (vibrator{r_arrow}rotor) transition and an O(6) nucleus ({gamma}-soft nucleus), but that the octupole fragmentation has an enhanced sensitivity to the d-boson composition of the wave functions and thereby reveals differences in structure that are not easily discernible with other observables. {copyright} {ital 1997} {ital The American Physical Society}

$J^{\pi}$= 0$^+$ states have been investigated in the actinide nucleus ${}^{240}$Pu up to an excitation energy of 3 MeV with a high-resolution (p,t) experiment at $E_{p}$= 24 MeV. To test the recently proposed $J^{\pi}$= 0$^+_2$ double-octupole structure, the phenomenological approach of the spdf-interacting boson model has been chosen. In addition, the total 0$^+$ strength distribution and the $0^+$ strength fragmentation have been compared to the model predictions as well as to the previously studied (p,t) reactions in the actinides. The results suggest that the structure of the 0$^+_2$ states in the actinides might be more complex than the usually discussed pairing isomers. Instead, the octupole degree of freedom might contribute significantly. The signature of two close-lying 0$^+$ states below the 2-quasiparticle energy is presented as a possible manifestation of strong octupole correlations in the structure of the 0$^+_2$ states in the actinides., Comment: 6 pages, 5 figures, published in Phys. Rev. C 88, 041303(R) (2013)

Excited states in ${}^{129}$I were populated with the ${}^{124}$Sn(${}^{7}$Li,$2n$) reaction at 23 MeV. In-beam measurements of $\ensuremath{\gamma}$-ray coincidences were performed with an array of eight HPGe detectors and five LaBr${}_{3}$(Ce) scintillation detectors. Based on the $\ensuremath{\gamma}\ensuremath{\gamma}$ coincidence data, a positive parity band structure built on the $7/{2}^{+}$ ground state was established and the $\ensuremath{\pi}{g}_{7/2}$ configuration at oblate deformation was assigned to it. The results are compared to interacting Boson-Fermion model (IBFM) and total Routhian surface (TRS) calculations.

The half-life of the Iπ=6+ yrast state at Ex=2294 keV in 138Ce has been measured as T1/2=880(19) ps using the fast-timing γ-ray coincidence method with a mixed LaBr3(Ce)-HPGe array. The excited states in 138Ce have been populated by the 130Te(12C,4n) fusion-evaporation reaction at an incident beam energy of 56 MeV. The extracted B(E2;61+→41+)=0.101(24) W.u. value is compared with the predictions of truncated basis shell model calculations and with the systematics of the region. This shows an anomalous behavior compared to the neighboring isotonic and isotopic chains. Half-lives for the yrast 5-, 11+ and 14+ states in 138Ce have also been determined in this work.

An extensive process of modernizing the research infrastructure started 6 years ago at the tandem accelerator in IFIN-HH. Major improvements of the 9 MV FN tandem accelerator installed in IFIN-HH in ′73 were done in the late years, making it a very reliable machine, suited for basic and applied research experiments. The developments opened the way for new experiments made for the first time in our laboratory. Two new Cockroft-Walton tandem accelerators were also installed in 2012. The 1 MV HVE Tandetron accelerator is dedicated to AMS measurements, especially for 14C dating, while the 3 MV HVE Tandetron accelerator has the reaction chambers and detection system prepared for ion beam analysis measurements, microprobe experiments and ion implantation.

The evolution of collective nuclear structure is discussed from a horizontal perspective, that is, as a function of the number of valence protons and neutrons. Starting from an explicit recognition of the importance of the valence residual p - n interaction in the equilibrium shape and structure of nuclei, the phenomenological scheme is presented, and validated via an analysis of empirical p - n interaction strengths. Applications of the scheme are presented which exploit this paradigm of structural evolution. The physics underlying occasional deviations from the scheme is extracted and new signatures of structure and of nuclear shape components are developed which will be useful for the study of exotic nuclei with radioactive beams. Finally, the smooth correlations of many observables with leads to a study of the correlations between different collective observables themselves. The remarkable results stemming from this approach are summarized.

A recently proposed correlation of quasiground band energies in collective nuclei is shown to provide a highly sensitive indicator of different classes of nuclei and to lead to an empirical analytic formula for these energies. {copyright} {ital 1996 The American Physical Society.}

A method for setting ${\mathrm{\ensuremath{\epsilon}}}_{\mathit{f}}$, one of the parameters in the interacting boson approximation-1 (IBA-1) with one f boson, by using the systematic behavior of the centroids of observed E3 strength is proposed and applied to obtaining fits for octupole bands in the deformed rare earth region. The ordering of bands with different K values, B(E3) strengths and B(E1) values are well reproduced. The calculations are in good agreement with the data in nearly all the K=0, 1, and 2 octupole bands examined here. The least satisfactory fits were obtained for the ${\mathit{K}}^{\mathrm{\ensuremath{\pi}}}$=${0}^{\mathrm{\ensuremath{-}}}$ bands in $^{160,162}\mathrm{Dy}$. It is predicted that in $^{160,162,164}\mathrm{Dy}$, $^{168}\mathrm{Er}$, and $^{172}\mathrm{Yb}$ the K=3 octupole states based on the ground state and having significant E3 strength are above 6 MeV and are strongly fragmented. These results are quite different from predictions made previously. \textcopyright{} 1996 The American Physical Society.

All known unique parity structures in precollective odd-A nuclei (having cores with E(4 1 + ) E(2 1 + ) ) are shown to behave similarly to the yrast quasibands in the neighboring even-even nuclei. This is interpreted in terms of a pair addition mode. With previous results on collective nuclei, this gives a tripartite classification of the evolution of the unique parity quasibands in odd-A nuclei. A simple index for signature splitting is also developed which avoids the need for complex analysis of Routhian structures.

The experimental values of both branching ratios and hindrance factors for the alpha decay of even-even trans-lead nuclei, corresponding to the ${2}_{1}^{+}$, ${4}_{1}^{+}$, and ${6}_{1}^{+}$ excited states in the daughter nucleus, are examined within the valence correlation scheme. Existing calculations do not reproduce certain conspicuous features of these data in the deformed nuclei region, thus leaving open the question of what details of nuclear structure in this region are responsible for these effects.

Y. Oktem,1 D. L. Balabanski,2 B. Akkus,1 L. Amon Susam,1 L. Atanasova,2 C. W. Beausang,3,4 R. B. Cakirli,1,5 R. F. Casten,3 M. Danchev,6,7 M. Djongolov,6,7 E. Ganioglu,1 K. A. Gladnishki,7 J. Tm. Goon,8 D. J. Hartley,6,9 A. A. Hecht,3,10 R. Krucken,3,11 J. R. Novak,3 G. Rainovski,7 L. L. Riedinger,6 T. Venkova,2 I. Yigitoglu,12 N. V. Zamfir,3,13 and O. Zeidan6 1Department of Physics, Istanbul University, Vezneciler, 34134, Istanbul, Turkey 2Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, BG-1784 Sofia, Bulgaria 3Wright Nuclear Structure Laboratory, Yale University, New Haven, Connecticut 06520, USA 4Department of Physics, University of Richmond, Richmond, Virginia 23173, USA 5Max-Planck-Institut fur Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg, Germany 6Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA 7Faculty of Physics, St. Kliment Ohridski University of Sofia, BG-1164 Sofia, Bulgaria 8Louisiana State University Department of Physics and Astronomy 202 Nicholson Hall, Tower Drive, Baton Rouge, Louisiana 70803-4001, USA 9Department of Physics, U.S. Naval Academy, Annapolis, Maryland 21402, USA 10Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA 11TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia V6T 2A3, Canada 12Gaziosmanpasa University, Science Faculty, Turkey 13National Institute for Physics and Nuclear Engineering, Bucharest-Magurele, Romania (Received 14 July 2012; published 12 November 2012)

It is shown that hexadecapole deformations can be estimated from B(E2; 21+ → 01+) values alone. Application of this method in the actinide nuclei gives semi-quantitative β4 values for 250,252Cf. A comparison with theoretical values provides general insight into the relative roles of shell gaps at Z = 114 and 126 which are important for the binding and stability of the heaviest nuclei.

A relation is presented stating that a sum of certain products of E2 matrix elements connecting the 0+ and 2+ levels in the ground, β-, and γ-bands in the limit of strong quadrupole deformation vanishes. As a consequence β → g E2 matrix elements are much smaller than β → γ matrix elements, contrary to the naive expectation based on the vibrational picture of independent β and γ excitations. This relation is supported by experimental data on deformed nuclei, and suggests a re-examination of the traditional understanding of these basic collective modes and their inter-relationships.

The recently discovered nearly universal anharmonic vibrator behavior (with {ital constant} anharmonicity) of nuclei with {ital E}(4{sub 1}{sup +})/{ital E}(2{sub 1}{sup +}) between 2.0 and 3.15 has been shown to be a natural and nearly automatic outcome of numerical interacting boson approximation (IBA) calculations. Here, we present an approximate analytic derivation and discussion of this based on the idea of the {ital Q} phonon.

The distribution of rotational energy spacings for low-spin yrast states in over two thousand pairs of deformed rare-earth even-even nuclei are studied to determine key factors that correlate with the moments of inertia. Nuclei with near identical [ital P] values ([ital P]=[ital N][sub [ital p]]N[sub [ital n]]/[[ital N][sub [ital p]]+[ital N][sub [ital n]]] where [ital N][sub [ital p]] and [ital N][sub [ital n]] are the numbers of valence protons and valence neutrons) are more than an order of magnitude more likely to show near identical bands than nuclei with different [ital P] values. This is, by far, the highest correlation found: no other variable is even 20% as effective. The statistical significance of these large [ital P] enhancements and the special relation between [ital P] and ground-state mean-field structures is confirmed by a complementary analysis of negative parity near identical bands, which show no [ital P] enhancement at all.

The structure of $^{122}\mathrm{Cd}$ was studied through the decay of $^{122}\mathrm{Ag}$ by \ensuremath{\gamma}-\ensuremath{\gamma} coincidences, \ensuremath{\gamma}-ray angular correlations, and \ensuremath{\beta}-\ensuremath{\gamma}-\ensuremath{\gamma} fast electronic scintillation timing (FEST) measurements. The phonon and intruder structure of the ${0}^{+}$ states is discussed. The energy systematics of the low-lying levels in the Cd isotopes exhibits two distinct patterns, one minimizing at midshell, one somewhat later.

Recent studies have shown that the phenomenology of single-magic and near-magic nuclei has universal characteristics analogous to those of collective nuclei and that, moreover, this phenomenology attaches smoothly to that describing collective nuclei. This has led to a number of new signatures of structure as well as to a new, tripartite, classification of nuclear structure that embraces the gamut of structures from magic, through pre-collective, to fully collective and rotational nuclei. Aside from the natural appeal of simple global correlations of collective observables, these results have particular significance for soon-to-be accessible exotic nuclei near the drip lines since they rely on only the simplest-to-obtain data, in particular, the energies of just the first two excited states, E(41+) and E(21+), of even-even nuclei, and the B(E2: 21+ → 01+) value. Indeed, without the need for more extensive level schemes, these basic data alone can reveal information about the goodness of seniority, about the validity of pair-addition mode relationships of adjacent even-even nuclei, about underlying shell structure (validity of magic numbers) and even about the shell model potential itself (e.g., the strengths of the l s and l2 terms).

Background: The pygmy dipole resonance (PDR) is an interesting nuclear structure phenomenon with an impact in predicting different astrophysics scenarios, for example, specific properties of neutron stars that can be determined from the thickness of the neutron skin which is directly connected to the strength of the PDR. Various collective and microscopic models were employed in order to account for the observed properties of the PDR.Purpose: Determine for the first time whether it is possible to use the interacting boson approximation (IBA) to reproduce the general characteristics of the PDR.Methods: The PDR properties of the stable even-even $N=82$ isotones are calculated in the IBA-$spdf$ model based on the assumption that many effects of the mixing caused by the shell structure can be simulated by considering the number of bosons as an effective value.Results: The IBA calculations indicate a resonance-like structure of the $E1$ strength in the energy region 5--8 MeV, thus confirming the experimental results for this mass region. The distribution and fragmentation of the ${J}^{\ensuremath{\pi}}={1}^{\ensuremath{-}}$ states and of the $E1$ strength are in good agreement with the experimental data. By employing the same procedure as for the $N=82$ isotones, the model is used to predict the PDR strength for a nucleus in a different mass region, i.e., for the ${}^{94}$Mo nucleus.Conclusions: The calculations confirm a good agreement for the distribution and fragmentation of the $E1$ strength.

The half-life of the 2305-keV, Iπ=4(−) intruder state in 34P has been measured as t1/2=2.0(1) ns using γ-ray coincidence, fast-timing techniques with the Bucharest HPGe and LaBr3:Ce detector array. Excited states in 34P were populated using the 18O(18O,pn)34P fusion-evaporation reaction at a beam energy of 36 MeV. Reduced transition probabilities have been calculated for different values of the M2/E3 mixing ratio, δE3/M2, and compared with shell-model estimates. For small values of the mixing ratio, the B(M2) value was found to be consistent with similar transitions associated with the occupation of neutron f7/2 configurations in this mass region.

The knowledge of excited states in the odd-odd ${}^{150}$Pm, completely unknown until recently, is important both for understanding double $\ensuremath{\beta}$ decay of ${}^{150}$Nd and for nuclear structure studies in mass regions with a quantum phase transition. A large number of excited states have been determined for the first time in this nucleus by measuring spectra of the ${}^{152}$Sm($d$,$\ensuremath{\alpha}$) direct reaction at 25 MeV with the Munich Q3D spectrograph and by $\ensuremath{\gamma}$-ray spectroscopy with the ($p,n\ensuremath{\gamma}$) reaction at 7.1 MeV at the Bucharest tandem accelerator. Some of these levels correspond to peaks recently observed with the ${(}^{3}$He,$t$) reaction at 140 MeV/u.

The low-spin excitations of the nucleus 146Sm which is just two neutrons and two protons away from the N = 82 shell and Z = 64 subshell closures have been investigated by means of the 143Nd (α, n) and 144Nd (α, 2n) fusion-evaporation reactions. We established 47 hitherto unknown energy levels up to 4.7MeV and 75 new transitions. In addition, 7 spin assignments were possible from the γ-γ angular correlation analysis. The structure of the possible candidates for a 2+ ⊗ 3− quadrupole-octupole multiplet are first discussed in terms of the harmonic vibrational model. A comparison of these states with the corresponding ones in the neighboring N = 84 isotones is also presented. Finally, the structure of the 146Sm nucleus is interpreted in terms of the IBA-spdf model. It is shown that the model is able to reproduce the experimental relative transition strengths of the 2+ ⊗ 3− quadrupole-octupole multiplet and also a series of collective properties such as the proposed double-octupole excitations.

Excited states in the 240Pu nucleus have been studied by means of the (p,t) reaction using the Q3D spectrometer and the focal plane detector from Munich. The comparison between experimental angular distributions and the DWBA calculations allowed the extraction of relative two-neutron transfer strengths. These observables may reveal important information about the structure of different states. The experimental two neutron strength for the 0+2 and 0+3 states is found in good agreement with the predictions of the IBA model, confirming the double octupole nature for the 0+2 state proposed in the previous studies.

WOS: 000300864200005, The Advanced GAmma Tracking Array (AGATA) is a European project to develop and operate the next generation gamma-ray spectrometer. AGATA is based on the technique of gamma-ray energy tracking in electrically segmented high-purity germanium crystals. This technique requires the accurate determination of the energy, time and position of every interaction as a gamma ray deposits its energy within the detector volume. Reconstruction of the full interaction path results in a detector with very high efficiency and excellent spectral response. The realisation of gamma-ray tracking and AGATA is a result of many technical advances. These include the development of encapsulated highly segmented germanium detectors assembled in a triple cluster detector cryostat, an electronics system with fast digital sampling and a data acquisition system to process the data at a high rate. The full characterisation of the crystals was measured and compared with detector-response simulations. This enabled pulse-shape analysis algorithms, to extract energy, time and position, to be employed. In addition, tracking algorithms for event reconstruction were developed. The first phase of AGATA is now complete and operational in its first physics campaign. In the future AGATA will be moved between laboratories in Europe and operated in a series of campaigns to take advantage of the different beams and facilities available to maximise its science output. The paper reviews all the achievements made in the AGATA project including all the necessary infrastructure to operate and support the spectrometer. (C) 2011 Elsevier B.V. All rights reserved., EU [RII3-CT-2004-506065]; German BMBF [06K-167, 06KY2051]; Swedish Research Council; Knut and Alice Wallenberg Foundation; UK EPSRC Engineering and Physical Sciences Research Council; UK STFC Science and Technology Facilities Council; AWE plc; Scientific and Technological Research Council of Turkey [106T055]; Ankara University [05B4240002]; Polish Ministry of Science and Higher Education [DPN/N190/AGATA/2009]; Spanish MICINN [FPA2008-06419, FPA2009-13377-C02-02]; Spanish Consolider-Ingenio Programme CPAN [CSD2007-00042]; Generalitat Valenciana [PROMETEO/2010/101]; MICINN, Spain; INFN, Italy [AIC10-D-000568]; Science and Technology Facilities Council [ST/F012039/1, ST/J000094/1, ST/F004192/1, ST/J000159/1, ST/I504940/1, NuSTAR, ST/F006950/1, ST/I504916/1, ST/G000670/1, ST/F004060/1, ST/J000051/1, ST/J000108/1, ST/G000670/1 NuSTAR, ST/I504959/1, ST/G000727/1, ST/F004052/1, ST/F004184/1], AGATA and this work is supported by the European funding bodies and the EU Contract RII3-CT-2004-506065, the German BMBF under Grants 06K-167 and 06KY2051, the Swedish Research Council and the Knut and Alice Wallenberg Foundation, UK EPSRC Engineering and Physical Sciences Research Council, UK STFC Science and Technology Facilities Council, AWE plc, Scientific and Technological Research Council of Turkey (Proj. nr. 106T055) and Ankara University (BAP Proj. nr. 05B4240002), the Polish Ministry of Science and Higher Education under Grant DPN/N190/AGATA/2009, the Spanish MICINN under grants FPA2008-06419 and FPA2009-13377-C02-02, the Spanish Consolider-Ingenio 2010 Programme CPAN (contract number CSD2007-00042) the Generalitat Valenciana under Grant PROMETEO/2010/101, and research performed in the frame of the GSI-IN2P3 collaboration agreement number 02-42. A. Gadea and E. Farnea acknowledge the support of MICINN, Spain, and INFN, Italy, through the AIC10-D-000568 bilateral action.

8th Topical Meeting on Industrial Radiation and Radioisotope Measurement Applications (IRRMA) -- JUN 24-JUL 01, 2011 -- Kansas City, MO WOS: 000306937800064 PubMed ID: 22154387 We report on a gamma-ray coincidence analysis using a mixed array of hyperpure germanium and cerium-doped lanthanum tri-bromide (LaBr3:Ce) scintillation detectors to study nuclear electromagnetic transition rates in the pico-to-nanosecond time regime in P-33,P-34 and S-33 following fusion-evaporation reactions between an O-18 beam and an isotopically enriched O-18 implanted tantalum target. Energies from decay gamma-rays associated with the reaction residues were measured in event-by-event coincidence mode, with the measured time difference information between the pairs of gamma-rays in each event also recorded using the ultra-fast coincidence timing technique. The experiment used the good full-energy peak resolution of the LaBr3:Ce detectors coupled with their excellent timing responses in order to determine the excited state lifetime associated with the lowest lying, cross-shell, I-pi = 4(-) "intruder" state previously reported in the N=19 isotone P-34. The extracted lifetime is consistent with a mainly single-particle M2 multipolarity associated with a f(7/2) -> d(5/2) single particle transition. (C) 2011 Elsevier Ltd. All rights reserved. Kansas State Univ (KSU), Coll Engn, KSU, Dept Mech & Nucl Engn, KSU, Radiat Measurement Applicat Lab, N Carolina Sate Univ, Ctr Engn Applicat Radiosotopes, Int Radiat Phys Soc (IRPS) Science and Technology Facilities Council [ST/J000051/1, ST/F006950/1, ST/G000751/1 NuSTAR, ST/G000751/1]

7Li induced-reactions have been used with a 186W target to populate nuclei around A∼180-190 at the National Institute of Physics and Nuclear Engineering in Bucharest, Romania. An array of high-purity germanium (HPGe) and cerium-doped lanthanum bromide (LaBr3:Ce) detectors have been used to measure sub-nanosecond half-lives with fast-timing techniques. The yrast 2+ state in 190Os was measured to be t1/2 = 375(20)ps, in excellent agreement with the literature value. The previously unreported half-life of the 564-keV state in 189Ir has also been measured and a value of t1/2 = 540(100)ps ps obtained.

It is shown that the remarkable nearly-universal anharmonic vibrator behavior recently discovered for yrast states in collective non-rotational nuclei is naturally reproduced by the IBA. The results shed light on the microscopic basis for the IBA.

A study of γ-band levels from Z = 30–82 allows an extension of a nearly-universal anharmonic vibrator description of nuclei to non-yrast states and shows that a multi-phonon picture gives an excellent description of the data.

The evolution of structure in pre-collective nuclei from oxygen to actinides is studied in terms of the structural signature R 4 2 ≡ E(4 + 1 ) E(2 + 1 ) in singly magic nuclei. A simple physical interpretation of these empirical trends is discussed in terms and illustrated with schematic shell model calculations. The basic idea does not depend on details of the calculations but rather invokes only very general features of nuclear shell structure and the fact that the nuclear force is short-range and attractive.

The Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory has recently produced the world's first post-accelerated beams of heavy neutron-rich nuclei. The first experiments with these beam are described, and the results discussed. B(E2;0+ → 2+) values for neutron-rich 126,128Sn and 132,134,136Te isotopes have been measured by Coulomb excitation in inverse kinematics. The results for 132Te and 134Te (N = 80, 82) show excellent agreement with systematics of lighter Te isotopes, but the B(E2) value for 136Te (N = 84) is unexpectedly small. Single-neutron transfer reactions with a 134Te beam on natBe and 13C targets at energies just above the Coulomb barrier have also been studied.

The ${2}_{2}^{+}$ state in ${}^{132}$Te is identified as the one-phonon mixed-symmetry state in a projectile Coulomb excitation experiment presenting a firm example of a mixed-symmetry state in unstable, neutron-rich nuclei. The results of shell-model calculations based on the low-momentum interaction ${V}_{\mathrm{low}\ensuremath{-}k}$ are in good agreement with experiment demonstrating the ability of the effective shell-model interaction to produce states of mixed-symmetry character.

Fast-timing measurements were performed in the region of the medium-mass $^{103,105,107}\mathrm{Cd}$ isotopes, produced in fusion evaporation reactions. Results on new and reevaluated half-lives are analyzed within a systematic study of transition rates. The $7/{2}_{1}^{+}$ states in $^{103,105,107}\mathrm{Cd}$ are interpreted as arising from a single-particle excitation. The $9/{2}^{+}$ states configuration assignment is based on the observed decay branches.

The cross sections of the {sup 115}Sn({alpha},{gamma}){sup 119}Te, {sup 115}Sn({alpha},n){sup 118}Te, and {sup 116}Sn({alpha},n){sup 119}Te reactions (both on ground and isomeric states) have been measured at effective center-of-mass energies from 9.3 to 14.8 MeV. During a first experiment, enriched self-supporting {sup 115}Sn (51.2%) + {sup 116}Sn (24.4%) foils were bombarded with an {alpha} beam delivered by the Bucharest IFIN-HH Tandem Accelerator. In a second experiment, a highly enriched {sup 116}Sn target was irradiated in order to disentangle the experimental cross section contributions due to {sup 115}Sn({alpha},{gamma}){sup 119}Te and {sup 115}Sn({alpha},n){sup 118}Te reactions obtained in the first measurement. The beam-induced activity was measured with two large volume HPGe detectors in close geometry. The experimental results were compared with theoretical predictions obtained in the framework of the statistical model.

$\ensuremath{\gamma}$ rays were measured at several angles in both singles and coincidence modes in the $^{115}\mathrm{Sn}$$(\ensuremath{\alpha},n\ensuremath{\gamma}){}^{118}$Te reaction at 15 MeV on a thick target. Multipolarities and mixing ratios were determined from the $\ensuremath{\gamma}$-ray angular distribution analysis. Lifetimes of 11 low- and medium-spin excited states in $^{118}\mathrm{Te}$ were determined from a Monte Carlo Doppler-shift attenuation method analysis of the Doppler broadened line shapes of $\ensuremath{\gamma}$ rays deexciting the levels. The results are discussed in comparison with the predictions of the interacting boson model.

The upcoming γ facilities MEGa-Ray (Livermore) and ELI-NP (Bucharest) will have a 10 5 times higher γ flux F 0 = 10 13 /s and a ~30 times smaller band width (ΔE γ /E γ = BW ≈ 10 -3 ) than the presently best γ beam facility. They will allow to extract a small γ beam of about 30 - 100 μm radius 1 m behind the γ production point, containing the dominant γ energy band width. One can collimate the γ beam down to Θ BW = √ BW/ γe , where γe = E e / m e c 2 is a measure of the energy E e of the electron beam, from which the γ beam is produced by Compton back-scattering. Due to the γ energy - angle correlation, the angular collimation results at the same time in a reduction of the γ beam band width without loss of "good" γ quanta, however, the primary γ flux F 0 is reduced to about F coll ≈ F 0 · 1.5 · ΔE γ /E γ . For γ rays in the (0.1-100) MeV range, the negative real part δ of the index of refraction n = 1- δ + i β from coherent Rayleigh scattering (virtual photo effect) dominates over the positive δ contributions from coherent virtual Compton scattering and coherent virtual pair creation scattering (Delbruck scattering). The very small absolute value |δ| ≈ 10 -6 - 10 -9 of the index of refraction of matter for hard X-rays and γ-rays and its negative sign—in contrast to usual optics—results in a very different γ-ray optics, e.g. focusing lenses become concave and we use stacks of N optimized lenses. It requires very small radii of curvature of the γ lenses and thus very small γ beam radii. This leads to a technical new solution, where the primary γ beam is subdivided into M γ beamlets, which do not interfere with each other, but contribute with their independent intensities. We send the γ beamlets into a two-dimensional array of closely packed cylindrical parabolic refractive lenses, where N ≈ 10 3 lenses with very small radius of curvature are stacked behind each other, leading to contracted beam spots in one dimension. With a second 1D lens system turned by 90 0 , we can obtain small spots for each of the beamlets. While focusing the beamlets to a much smaller spot size, we can bend them effectively with micro wedges to e.g. parallel beamlets. We can monochromatize these γ beamlets within the rocking curve of a common Laue crystal, using an additional angle selection by a collimator to reach a strongly reduced band width of 10 -4 - 10 -6 . We propose the use of a further lens/wedge arrays or Bragg reflection to superimpose the beamlets to a very small total γ beam spot. Many experiments gain much from the high beam resolution and the smaller focal spot. This new γ optics requires high resolution diagnostics, where we want to optimize the focusing, using very thin target wires of a specific nuclear resonance fluorescence (NRF) isotope to monitor the focusing for the resonance energy. With such beams we can explore new nuclear physics of higher excited states with larger level densities. New phenomena, like the transition from chaotic to regular nuclear motion, weakly-bound halo states or states decaying by tunneling can be studied. The higher level density also allows to probe parity violating nuclear forces more sensitively. This γ optics improves many applications, like a more brilliant positron source, a more brilliant neutron source, higher specific activity of medical radioisotopes or NRF micro-imaging.

Half-lives of the 19/2+ and 21/2+ states in 95Mo and of the 8+ and 10+ states in 96Mo were measured. Matrix elements for yrast transitions in 95Mo and 96Mo are discussed., Comment: Proceedings of XIX International School on Nuclear Physics, Neutron Physics and Applications, Varna, Bulgaria, 2011, 5 pages, 6 figures

The energies of [Formula: see text] states in even-even nuclei from Dy to W are shown to be linear in the P-factor and can be described using the same slope prescription for all these nuclei. Deviations are found for Os and Pt isotopes with Np. The results for N>104 give evidence for a more complex structural evolution beyond midneutron shell.

The Doppler shifts of \ensuremath{\gamma} rays following the decay of the ${1}_{1}^{\mathrm{\ensuremath{-}}}$ and ${3}_{1}^{\mathrm{\ensuremath{-}}}$ states in $^{150,152,154}\mathrm{Sm}$ excited by inelastic scattering of 1.3 MeV neutrons from natural ${\mathrm{Sm}}_{2}$${\mathrm{O}}_{3}$ have been measured. With the Winterbon theory to describe the slowing down process of the recoiling atoms in the bulk of the target material, nuclear lifetimes could be extracted from these data. These measured lifetimes are compared to the results of a recent investigation with the gamma-ray induced Doppler (GRID) broadening technique and have been used to clarify problems associated with the incomplete knowledge of the feeding pattern in heavy nuclei inherent in the GRID method. The large E1 transition rates in $^{152}\mathrm{Sm}$ obtained in the previous study are confirmed; the B(E1) systematics has been extended to $^{154}\mathrm{Sm}$ and is interpreted within the framework of the interacting boson model.

The [ital g] factor of the first excited, 3/2[sup +], 93.6 keV level of [sup 91]Sr was measured using a beam of separated fission products and the time-differential perturbed angular correlation method. The result, [ital g](3/2[sup +])=[minus]0.231(11), is discussed in the context of the systematics of [ital g] factors of [ital N]=53--57 isotones, and found to be in good agreement with the prediction of the core-excitation model.

A new analysis of yrast energies in collective medium and heavy even-even nuclei shows two startling results. First, although these nuclei exhibit widely varying structure [the ratio [ital E](4[sub 1][sup +])/[ital E](2[sub 1][sup +]) ranges from [similar to]2.0 to [similar to]3.33], they show a universal behavior of an [ital anharmonic] [ital vibrator] with [ital nearly] [ital constant] [ital anharmonicity] in which the multiphonon interactions are independent of the internal structure of the vibration. Second, the transition from anharmonic vibrator to rotor can be described by [ital critical] [ital phase] [ital transitional] [ital behavior]. These results suggest a reexamination of very basic ideas of structural evolution in finite-body nuclear systems.

The 2-tracked empirical correlation between B (E2; 2 1 + → 0 1 + ) and E(4 1 + )/E(2 1 + ) values is shown to exemplify the different ways yrast transition rates and energy levels sample collectivity. Model calculations for transitional nuclei show that this correlation provides a simple new signature to distinguish the two principal classes of nuclear shape transitions.

The lifetimes of the lowest ${3}^{\mathrm{\ensuremath{-}}}$ and ${1}^{\mathrm{\ensuremath{-}}}$ states in $^{148\mathrm{\ensuremath{-}}152}\mathrm{Sm}$ have been determined employing the gamma-ray-induced Doppler broadening technique. The B(E1;${3}^{\mathrm{\ensuremath{-}}}$\ensuremath{\rightarrow}${2}^{+}$) transition rates are compared to the corresponding B(E1;${1}^{\mathrm{\ensuremath{-}}}$\ensuremath{\rightarrow}${0}^{+}$) values and interpreted in the framework of the interacting boson approximation sdf model. The qualitative behavior of these absolute transition rates can be understood in a simple physical picture by considering only the one-body part in the E1 transition operator. A more complex form including two-body terms is needed to explain simultaneously all available experimental data related to these levels.

We propose a simple systematics of low-lying 2{sub 1}{sup +} energy levels and electromagnetic transitions in semimagic isotopic chains Z=28,50,82 and isotonic chains N=28,50,82,126. To this purpose we use a two-level pairing plus quadrupole Hamiltonian, within the spherical quasiparticle random phase approximation (QRPA). We derive a simple relation connecting the 2{sub 1}{sup +} energy with the pairing gap and quadrupole-quadupole (QQ) interaction strength. It turns out that the systematics of energy levels and B(E2) values predicted by this simple model is fulfilled with a reasonable accuracy by all available experimental data. This systematics suggests that not only active nucleons but also those filling closed shells play an important role.

The interacting boson approximation (IBA) is employed in the present article to follow the structural evolution of the neutron-deficient nuclei from the $Z=52--62$ region. The IBA model parameters are determined to reproduce the properties of the low-lying positive parity excitations for a wide range of even-even collective nuclei. The parameters aim to describe simultaneously the existing electromagnetic data (energy levels, transition matrix elements, etc.) and hadronic ones (two-nucleon transfer intensities). It is shown that a simple Hamiltonian with only two terms is not adequate to describe the properties across this region. It is found that the octupole term plays an important role in reproducing the properties of the ${2}_{\ensuremath{\gamma}}^{+}$ and ${0}_{2}^{+}$ states, as well as in the description of the two-neutron transfer intensities patterns. A mapping of these parameters in the IBA symmetry triangle allows the comparison of representative trajectories for different isotopic chains.

{gamma} rays were measured at several angles in both singles and coincidence mode in the {sup 119}Sn({alpha},n{gamma}){sup 122}Te reaction at 15 MeV on a thick target. Lifetimes of excited states in {sup 122}Te were determined from a Monte Carlo Doppler shift attenuation method (DSAM) analysis of the Doppler broadened lines shapes of {gamma} rays de-exciting the levels. A comparison of several deduced lifetimes with recent results obtained with the (n,n{sup '}) reaction allowed us to validate the choice of a parameter used to calculate the contribution of the side feeding times. The ingredients of the DSAM line-shape analysis (stopping power, description of instrumental line shapes, and side feeding evaluation) are presented in some detail. It is concluded that with proper treatment of side feeding, a DSAM line-shape analysis of peaks in singles or coincidence spectra obtained following the ({alpha},n{gamma}) reaction is able to provide rather accurate values for the lifetimes of levels with low and medium spins.

The low-lying excited states in $^{132,134}\mathrm{Ba}$ isotopes have been studied with high-resolution ($p,t$) reactions. The experiments were performed at the Munich Q3D spectrograph with a 25-MeV proton beam and the 1.5-m-long focal plane detector. The high-resolution triton spectra allowed the observation of levels up to $~4$ MeV. The experimental results revealed 75 excited states in $^{134}\mathrm{Ba}$ and 79 in $^{132}\mathrm{Ba}$, many of them observed for the first time. The measured angular distributions compared with distorted-wave Born approximation calculations allowed spin assignments for these levels in most cases. The systematics of the monopole and quadrupole two-neutron transfer strengths is compared with the prediction of the interacting boson approximation model. The results indicate a transitional structure in $^{132}\mathrm{Ba}$ and $^{134}\mathrm{Ba}$ and contribute additional evidence in favor of a description between the U(5) and O(6) symmetries of the model.