1,499 research outputs found

    Isotopic Production Cross Sections in Proton-Nucleus Collisions at 200 MeV

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    Intermediate mass fragments (IMF) from the interaction of 27^{27}Al, 59^{59}Co and 197^{197}Au with 200 MeV protons were measured in an angular range from 20 degree to 120 degree in the laboratory system. The fragments, ranging from isotopes of helium up to isotopes of carbon, were isotopically resolved. Double differential cross sections, energy differential cross sections and total cross sections were extracted.Comment: accepted by Phys. Rev.

    Studies of the Giant Dipole Resonance in 27^{27}Al, 40^{40}Ca, 56^{56}Fe, 58^{58}Ni and 208^{208}Pb with high energy-resolution inelastic proton scattering under 0^\circ

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    A survey of the fine structure of the Isovector Giant Dipole Resonance (IVGDR) was performed, using the recently commissioned zero-degree facility of the K600 magnetic spectrometer at iThemba LABS. Inelastic proton scattering at an incident energy of 200 MeV was measured on 27^{27}Al, 40^{40}Ca, 56^{56}Fe, 58^{58}Ni and 208^{208}Pb. A high energy resolution (ΔE\rm{\Delta}\it{E} \simeq 40 keV FWHM) could be achieved after utilising faint-beam and dispersion-matching techniques. Considerable fine structure is observed in the energy region of the IVGDR and characteristic energy scales are extracted from the experimental data by means of a wavelet analysis. The comparison with Quasiparticle-Phonon Model (QPM) calculations provides insight into the relevance of different giant resonance decay mechanisms. Photoabsorption cross sections derived from the data assuming dominance of relativistic Coulomb excitation are in fair agreement with previous work using real photons.Comment: 15 pages, 15 figure

    Single-atom doping for quantum device development in diamond and silicon

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    The ability to inject dopant atoms with high spatial resolution, flexibility in dopant species and high single ion detection fidelity opens opportunities for the study of dopant fluctuation effects and the development of devices in which function is based on the manipulation of quantum states in single atoms, such as proposed quantum computers. We describe a single atom injector, in which the imaging and alignment capabilities of a scanning force microscope (SFM) are integrated with ion beams from a series of ion sources and with sensitive detection of current transients induced by incident ions. Ion beams are collimated by a small hole in the SFM tip and current changes induced by single ion impacts in transistor channels enable reliable detection of single ion hits. We discuss resolution limiting factors in ion placement and processing and paths to single atom (and color center) array formation for systematic testing of quantum computer architectures in silicon and diamond

    Wavelet signatures of KK-splitting of the Isoscalar Giant Quadrupole Resonance in deformed nuclei from high-resolution (p,p') scattering off 146,148,150^{146,148,150}Nd

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    The phenomenon of fine structure of the Isoscalar Giant Quadrupole Resonance (ISGQR) has been studied with high energy-resolution proton inelastic scattering at iThemba LABS in the chain of stable even-mass Nd isotopes covering the transition from spherical to deformed ground states. A wavelet analysis of the background-subtracted spectra in the deformed 146,148,150Nd isotopes reveals characteristic scales in correspondence with scales obtained from a Skyrme RPA calculation using the SVmas10 parameterization. A semblance analysis shows that these scales arise from the energy shift between the main fragments of the K = 0, 1 and K = 2 components.Comment: 7 pages, 6 figure

    Fine structure of the isoscalar giant quadrupole resonance in 40Ca due to Landau damping?

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    The fragmentation of the Isoscalar Giant Quadrupole Resonance (ISGQR) in 40Ca has been investigated in high energy-resolution experiments using proton inelastic scattering at E_p = 200 MeV. Fine structure is observed in the region of the ISGQR and its characteristic energy scales are extracted from the experimental data by means of a wavelet analysis. The experimental scales are well described by Random Phase Approximation (RPA) and second-RPA calculations with an effective interaction derived from a realistic nucleon-nucleon interaction by the Unitary Correlation Operator Method (UCOM). In these results characteristic scales are already present at the mean-field level pointing to their origination in Landau damping, in contrast to the findings in heavier nuclei and also to SRPA calculations for 40Ca based on phenomenological effective interactions, where fine structure is explained by the coupling to two-particle two-hole (2p-2h) states.Comment: Phys. Lett. B, in pres

    Isoscalar giant monopole strength in 58^{58}Ni, 90^{90}Zr, 120^{120}Sn and 208^{208}Pb

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    Inelastic α\alpha-particle scattering at energies of a few hundred MeV and very-forward scattering angles including 00^\circ has been established as a tool for the study of the isoscalar giant monopole (IS0) strength distributions in nuclei. An independent investigation of the IS0 strength in nuclei across a wide mass range was performed using the 00^\circ facility at iThemba Laboratory for Accelerator Based Sciences (iThemba LABS), South Africa, to understand differences observed between IS0 strength distributions in previous experiments performed at the Texas A\&M University (TAMU) Cyclotron Institute, USA and the Research Center for Nuclear Physics (RCNP), Japan. The isoscalar giant monopole resonance (ISGMR) was excited in 58^{58}Ni, 90^{90}Zr, 120^{120}Sn and 208^{208}Pb using α\alpha-particle inelastic scattering with 196196 MeV α\alpha beam and scattering angles θLab=0\theta_{\text{Lab}} = 0^\circ and 44^\circ. The K600600 magnetic spectrometer at iThemba LABS was used to detect and momentum analyze the inelastically scattered α\alpha particles. The IS0 strength distributions in the nuclei studied were deduced with the difference-of-spectra (DoS) technique including a correction factor for the 44^\circ data based on the decomposition of L>0L > 0 cross sections in previous experiments. IS0 strength distributions for 58^{58}Ni, 90^{90}Zr, 120^{120}Sn and 208^{208}Pb are extracted in the excitation-energy region Ex=925E_{\rm x} = 9 - 25 MeV.Using correction factors extracted from the RCNP experiments, there is a fair agreement with their published IS0 results. Good agreement for IS0 strength in 58^{58}Ni is also obtained with correction factors deduced from the TAMU results, while marked differences are found for 90^{90}Zr and 208^{208}Pb.Comment: 12 pages, 10 figures, regular article submitted to PR

    Fine structure of the isoscalar giant monopole resonance in 58^{58}Ni, 90^{90}Zr, 120^{120}Sn and 208^{208}Pb

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    Over the past two decades high energy-resolution inelastic proton scattering studies were used to gain an understanding of the origin of fine structure observed in the isoscalar giant quadrupole resonance (ISGQR) and the isovector giant dipole resonance (IVGDR). Recently, the isoscalar giant monopole resonance (ISGMR) in 58^{58}Ni, 90^{90}Zr, 120^{120}Sn and 208^{208}Pb was studied at the iThemba Laboratory for Accelerator Based Sciences (iThemba LABS) by means of inelastic α\alpha-particle scattering at very forward scattering angles (including 00\circ). The good energy resolution of the measurement revealed significant fine structure of the ISGMR.~To extract scales by means of wavelet analysis characterizing the observed fine structure of the ISGMR in order to investigate the role of different mechanisms contributing to its decay width. Characteristic energy scales are extracted from the fine structure using continuous wavelet transforms. The experimental energy scales are compared to different theoretical approaches performed in the framework of quasiparticle random phase approximation (QRPA) and beyond-QRPA including complex configurations using both non-relativistic and relativistic density functional theory. All models highlight the role of Landau fragmentation for the damping of the ISGMR especially in the medium-mass region. Models which include the coupling between one particle-one hole (1p-1h) and two particle-two hole (2p-2h) configurations modify the strength distributions and wavelet scales indicating the importance of the spreading width. The effect becomes more pronounced with increasing mass number. Wavelet scales remain a sensitive measure of the interplay between Landau fragmentation and the spreading width in the description of the fine structure of giant resonances.Comment: 13 pages,7 figures, regular articl

    Народная культура и традиции

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    CITATION: Donaldson, L. M., et al. 2018. Deformation dependence of the isovector giant dipole resonance : theneodymium isotopic chain revisited. Physics Letters B, 776:133-138, doi:10.1016/j.physletb.2017.11.025.The original publication is available at https://www.sciencedirect.comProton inelastic scattering experiments at energy Ep=200MeV and a spectrometer scattering angle of 0° were performed on 144,146,148,150Nd and 152Sm exciting the IsoVector Giant Dipole Resonance (IVGDR). Comparison with results from photo-absorption experiments reveals a shift of resonance maxima towards higher energies for vibrational and transitional nuclei. The extracted photo-absorption cross sections in the most deformed nuclei, 150Nd and 152Sm, exhibit a pronounced asymmetry rather than a distinct double-hump structure expected as a signature of K-splitting. This behaviour may be related to the proximity of these nuclei to the critical point of the phase shape transition from vibrators to rotors with a soft quadrupole deformation potential. Self-consistent random-phase approximation (RPA) calculations using the SLy6 Skyrme force provide a relevant description of the IVGDR shapes deduced from the present data.https://www.sciencedirect.com/science/article/pii/S0370269317309176Publisher's versio

    Self Assembly and Properties of C:WO3 Nano-Platelets and C:VO2/V2O5 Triangular Capsules Produced by Laser Solution Photolysis

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    Laser photolysis of WCl6 in ethanol and a specific mixture of V2O5 and VCl3 in ethanol lead to carbon modified vanadium and tungsten oxides with interesting properties. The presence of graphene’s aromatic rings (from the vibrational frequency of 1,600 cm−1) together with C–C bonding of carbon (from the Raman shift of 1,124 cm−1) present unique optical, vibrational, electronic and structural properties of the intended tungsten trioxide and vanadium dioxide materials. The morphology of these samples shows nano-platelets in WOx samples and, in VOx samples, encapsulated spherical quantum dots in conjunction with fullerenes of VOx. Conductivity studies revealed that the VO2/V2O5 nanostructures are more sensitive to Cl than to the presence of ethanol, whereas the C:WO3 nano-platelets are more sensitive to ethanol than atomic C

    High-Energy-Resolution Inelastic Electron and Proton Scattering and the Multiphonon Nature of Mixed-Symmetry 2 States in 94 Mo

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    High-energy-resolution inelastic electron scattering (at the S-DALINAC) and proton scattering (at iThemba LABS) experiments permit a thorough test of the nature of proposed one-and two-phonon symmetric and mixed-symmetric 2 states of the nucleus 94 Mo. The combined analysis reveals the onephonon content of the mixed-symmetry state and its isovector character suggested by microscopic nuclear model calculations. The purity of two-phonon 2 states is extracted. DOI: 10.1103/PhysRevLett.99.092503 PACS numbers: 21.10.Re, 25.30.Dh, 25.40.Ep, 27.60.+j Collective valence-shell excitations are a generic feature of strongly-coupled mesoscopic quantum systems. A prime example of a two-component system is the atomic nucleus formed by protons and neutrons. The microscopic structure of collective nuclear excitations with respect to their proton-neutron content is a central issue of nuclear structure physics with general implications for the physics of composite strongly-coupled quantum systems. Low-energy nuclear valence-shell excitations usually possess the lowest possible isospin quantum number T < jN ÿ Zj=2. Nevertheless, the symmetry character of their proton-neutron coupling can vary. This fact is evident in the framework Recently, one-and two-phonon MSSs were investigated in vibrational nuclei with proton and neutron numbers near closed shells, e.g., in the nuclide 94 Mo [5]. Comprehensive spectroscopic information on low-spin states has been achieved up to an excitation energy of about 4 MeV It is the purpose of this Letter to report a combined study of electron and proton scattering differential cross sections for J 2 one-and two-phonon FSSs and MSSs in 94 Mo. The selectivity of both reactions to one-phonon components in the excited state wave functions allows to extract for the first time the small one-phonon contributions to the two-phonon candidates. The proton-neutron symmetry character can be derived since electron scattering couples to the proton distributions, while proton scattering is dominated by the isoscalar central part of the effective proton-nucleus interaction. We thereby introduce a new approach establishing a multiphonon character of nuclear MSSs based on scattering data complementary to -ray spectroscopy. The (e; e 0 ) experiments were carried out at the highenergy-resolution magnetic spectromete
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