Effect of large neutron excess on the dipole response in the region of the Giant Dipole Resonance

The evolution of the Dipole Response in nuclei with strong neutron excess is studied in the Hartree-Fock plus Random Phase Approximation with Skyrme forces. We find that the neutron excess increases the fragmentation of the isovector Giant Dipole Resonance, while pushing the centroid of the distribution to lower energies beyond the mass dependence predicted by the collective models. The radial separation of proton and neutron densities associated with a large neutron excess leads to non vanishing isoscalar transition densities to the GDR states, which are therefore predicted to be excited also by isoscalar nuclear probes. The evolution of the isoscalar compression dipole mode as a function of the neutron excess is finally studied. We find that the large neutron excess leads to a strong concentration of the strength associated with the isoscalar dipole operator $\sum_ir^3_iY_{10}$, that mainly originates from uncorrelated excitations of the neutrons of the skin.Comment: 11 pages 8 figures, use elsart.sty and graphics packag

Coupling of Surface and Volume Dipole Oscillations in C-60 Molecules

We first give a short review of the ``local-current approximation'' (LCA), derived from a general variation principle, which serves as a semiclassical description of strongly collective excitations in finite fermion systems starting from their quantum-mechanical mean-field ground state. We illustrate it for the example of coupled translational and compressional dipole excitations in metal clusters. We then discuss collective electronic dipole excitations in C$_{60}$ molecules (Buckminster fullerenes). We show that the coupling of the pure translational mode (``surface plasmon'') with compressional volume modes in the semiclasscial LCA yields semi-quantitative agreement with microscopic time-dependent density functional (TDLDA) calculations, while both theories yield qualitative agreement with the recent experimental observation of a ``volume plasmon''.Comment: LaTeX, 12 pages, 5 figures (8 *.eps files); Contribution to XIV-th Nuclear Physics Workshop at Kazimierz Dolny, Poland, Sept. 26-29, 200

Isovector Giant Dipole Resonance from the 3D Time-Dependent Density Functional Theory for Superfluid Nuclei

A fully symmetry unrestricted Time-Dependent Density Functional Theory extended to include pairing correlations is used to calculate properties of the isovector giant dipole resonances of the deformed open-shell nuclei 172Yb (axially deformed), 188Os (triaxially deformed), and 238U (axially deformed), and to demonstrate good agreement with experimental data on nuclear photo-absorption cross-sections for two different Skyrme force parametrizations of the energy density functional: SkP and SLy4.Comment: 5 pages, 3 figures, published versio

Excitation of soft dipole modes in electron scattering

The excitation of soft dipole modes in light nuclei via inelastic electron scattering is investigated. I show that, under the proposed conditions of the forthcoming electron-ion colliders, the scattering cross sections have a direct relation to the scattering by real photons. The advantages of electron scattering over other electromagnetic probes is explored. The response functions for direct breakup are studied with few-body models. The dependence upon final state interactions is discussed. A comparison between direct breakup and collective models is performed. The results of this investigation are important for the planned electron-ion colliders at the GSI and RIKEN facilities.Comment: 23 pages, 8 figures, to be published in Physical Review

Far infrared giant dipole resonances in neutral quantum dots

A resonance behaviour of the far infrared absorption probability at a frequency \sim N^{1/4} is predicted for clusters of N electron-hole pairs (2\le N\le 110) confined in disk-shaped quantum dots. For radially symmetric dots, the absorption is dominated by a Giant Dipole Resonance, which accounts for more than 98 % of the energy-weighted photoabsorption sum rule.Comment: final versio

Damping of giant resonances in asymmetric nuclear matter

The giant collective modes in asymmetric nuclear matter are investigated within a dynamic relaxation time approximation. We derive a coupled dispersion relation and show that two sources of coupling appear: (i) a coupling of isoscalar and isovector modes due to different mean-fields acting and (ii) an explicit new coupling in asymmetric matter due to collisional interaction. We show that the latter one is responsible for a new mode arising besides isovector and isoscalar modes.Comment: Varenna conference proceeding

Photonuclear reactions of actinides in the giant dipole resonance region

Photonuclear reactions at energies covering the giant dipole resonance (GDR) region are analyzed with an approach based on nuclear photoabsorption followed by the process of competition between light particle evaporation and fission for the excited nucleus. The photoabsorption cross section at energies covering the GDR region is contributed by both the Lorentz type GDR cross section and the quasideuteron cross section. The evaporation-fission process of the compound nucleus is simulated in a Monte-Carlo framework. Photofission reaction cross sections are analyzed in a systematic manner in the energy range of $\sim$ 10-20 MeV for the actinides $^{232}$Th, $^{238}$U and $^{237}$Np. Photonuclear cross sections for the medium-mass nuclei $^{63}$Cu and $^{64}$Zn, for which there are no fission events, are also presented. The study reproduces satisfactorily the available experimental data of photofission cross sections at GDR energy region and the increasing trend of nuclear fissility with the fissility parameter $Z^2/A$ for the actinides.Comment: 4 pages including 2 tables and 1 figur

Multiphonon Giant Resonances

A new class of giant resonances in nuclei is discussed, i.e., giant resonances built on other giant resonances. These resonances are observed with very large cross sections in relativistic heavy ion collisions. A great experimental and theoretical effort is underway to understand the reaction mechanism which leads to the excitation of these states in nuclei, as well as the better microscopic understanding of their properties, e.g., strength, energy centroids, widths, and anharmonicities.Comment: Postscript file with text and 11 embedded figure

The Impact of Cancer Caregiving on Cancer Caregivers: Stories of Lives in Transition

The purpose of the study was to examine the impact of cancer caregiving on primary caregivers, exploring their personal narratives looking back on the entire experience from diagnosis, through treatment, and beyond. Caregiving is associated with exacerbation of stress-related disorders such as hypertension and heart disease and may also be associated with increased mortality rates. Transitions theory served as the conceptual framework for the study. Eleven adult caregivers, pre-retirement age, each participated in two semi-structured interviews. Caregivers were recruited from a community cancer resource center and were purposively selected to achieve maximum variation in terms of outcome of cancer treatment. The sample included 8 females and 3 males; there were 3 husbands, 6 wives, and 2 daughters. Caregivers provided care for patients with a variety of cancer types and a variety of treatment outcomes, from cancer free with sequelae to deceased. Each caregiver interview recording was transcribed, and preliminary examination of each transcript helped guide subsequent interviews. NVivo9 software was used to assist with data management. Data saturation was achieved. Narrative within-case analyses as well as thematic analysis were used to address research questions. Thematic analysis resulted in seven themes: Burden: The Load that Never Ends; Disconnectedness and Isolation: The Invisible Person; Helplessness and Loss of Control: Tied to This Ride; Dealing with the Healthcare System; Role Disruption: Spinning the Plates; Loss, Change, and Grief: Reaction to the Whole; and Carrying Forward with Scars: New Priorities and Permanent Change. All of the caregivers changed their employment or social responsibilities due to the demands of caregiving. Themes were present in different parts of the cancer trajectory and in differing intensities in all interviews. Findings included disconnectedness and isolation as a central feature of cancer caregiving, plus significant grief present through the cancer trajectory, especially in the post-treatment phase. Furthermore, the experience of cancer caregiving remained one of significant impact years after treatment had ended. Successful transitioning requires connectedness and mastery, but participants in this study identified that their caregiving trajectories were full of isolation, grief, burden, and helplessness. Many suggested the need for support, even though they tended to deny their own physical and emotional needs while caregiving. Healthcare professionals can help by providing information, support, listening, and grief counselling. Research is needed on interventions that may reduce isolation, helplessness, and burden for caregivers