arXiv subjects

H. Garcia

Publications and source records attributed to H. Garcia.

6 recordsLinked to original sources

arXiv2018

The NUMEN project: NUclear Matrix Elements for Neutrinoless double beta decay

The article describes the main achievements of the NUMEN project together with an updated and detailed overview of the related R&D activities and theoretical developments. NUMEN proposes an innovative technique to access the nuclear matrix elements entering the expression of the lifetime of the double beta decay by cross section measurements of heavy-ion induced Double Charge Exchange (DCE) reactions. Despite the two processes, namely neutrinoless double beta decay and DCE reactions, are triggered by the weak and strong interaction respectively, important analogies are suggested. The basic point is the coincidence of the initial and final state many-body wave-functions in the two types of processes and the formal similarity of the transition operators. First experimental results obtained at the INFN-LNS laboratory for the 40Ca(18O,18Ne)40Ar reaction at 270 MeV, give encouraging indication on the capability of the proposed technique to access relevant quantitative information. The two major aspects for this project are the K800 Superconducting Cyclotron and MAGNEX spectrometer. The former is used for the acceleration of the required high resolution and low emittance heavy ion beams and the latter is the large acceptance magnetic spectrometer for the detection of the ejectiles. The use of the high-order trajectory reconstruction technique, implemented in MAGNEX, allows to reach the experimental resolution and sensitivity required for the accurate measurement of the DCE cross sections at forward angles. However, the tiny values of such cross sections and the resolution requirements demand beam intensities much larger than manageable with the present facility. The on-going upgrade of the INFN-LNS facilities in this perspective is part of the NUMEN project and will be discussed in the article.

nucl-ex↗

arXiv2013

Time Response Dynamics of Plasmon Excitation in Cobalt Nanoparticles on Glass Substrate

We use ultrafast pump-probe transmission spectroscopy to measure the electronic relaxation time for electrons in cobalt nanoparticles embedded on glass substrate using femtosecond laser pulses. We found that the plasmon excitation is inhomogenously broadening with a fast excitation time of 23 fs. and a plasmonic relaxation time of 97fs. The femtosecond laser pulses used in this experiment were come from a Ti:Sapphire resonator that uses a self-mode-locking mechanism based on the nonlinear Kerr effect. The pulses were found to have repetition rate of 103.52MHz with a pulse width of 64.5 fs at FWHM, and 810nm center wavelength.

physics.optics↗

arXiv2011

$uvby-β$ photoelectric photometry of the open clusters NGC 6811 and NGC 6830

From $uvby-β$ photometry of the open clusters NGC 6811 (75 stars), and NGC 6830 (19 stars) we were able to determine membership of the stars to each cluster, and fix the age and reddening for each. Since several short period stars have recently been found, we have carried out a study of these variables.

astro-ph.SR↗

arXiv2010

Design and optimization of plasmonic-based metal-dielectric nanocomposite materials for energy applications

Metallic nanoparticles embedded in dielectrics permit enhanced capture of light at specific wavelengths through excitation of plasmons, i.e. the quanta of coherent and collective oscillations of large concentrations of nearly free electrons. In order to maximize the potential of such enhanced absorption in useful tasks, such as the generation of carriers in photocatalysts and semiconductors, it is important to be able to predict and design plasmonic nanocomposites with desired wavelength-dependent optical absorption. Recently, a mixing approach formulated by Garcia and co-workers [Phys. Rev. B, 75, 045439 (2007)] has been successfully applied to model the experimentally measured broadband optical absorption for ternary nanocomposites containing alloys or mixtures of two metals (from Ag, Au or Cu) in SiO dielectric. In this work we present the broadband optical behavior of important optical coating dielectrics (SiN and SiO) and photocatalyst (TiO) containing various configuration of nanoparticles of Al, Au, Ag, or Cu. The spectral behavior of various combinations of the metallic species in the dielectrics was optimized to show either broadband solar absorption or strong multiple plasmonic absorption peaks. The applications of such nanocomposite materials in solar energy harvesting and spectral sensing are also presented and discussed.

cond-mat.mtrl-sci↗

arXiv2007

Neutron Transfer reactions induced by 8Li on 9Be

Angular distributions for the elastic scattering of 8Li on 9Be and the neutron transfer reactions 9Be(8Li,7Li)10Be and 9Be(8Li,9Li)8Be have been measured with a 27 MeV 8Li radioactive nuclear beam. Spectroscopic factors for 8Li|n=9Li and 7Li|n=8Li bound systems were obtained from the comparison between the experimental differential cross section and finite-range DWBA calculations with the code FRESCO. The spectroscopic factors obtained are compared to shell model calculations and to other experimental values from (d,p) reactions. Using the present values for the spectroscopic factor, cross sections for the direct neutron-capture reactions 7Li(n,g)8Li and 8Li(n,g)9Li were calculated in the framework of a potential model.

nucl-ex↗

arXiv2006

Nanostructure and microstructure of laser-interference induced dynamic patterning of Co on Si

We have investigated the nanostructure and microstructure resulting from ns laser irradiation simultaneous with deposition of Co films on Si(001) substrates. The spatial order and length scales of the resulting nanopatterns and their crystalline microstructure were investigated as a function of film thickness h and laser energy density E using a combination of atomic force, scanning electron and transmission electron microscopies. The results could be classified into two distinct categories based on the laser energy density used. It was observed that the thickness-dependent E required to melt the Co film (E_{Co}) was lower than Si (E_{Si}) primarily because of the higher reflectivity of Si. Consequently, for energy densities E_{Co}<E_{1}<E_{Si} that preferentially melted the Co film, spatially ordered nanoparticles were formed and were attributed to capillary-driven transport in the liquid phase. The ordering length scale corresponded to the interference fringe spacing Λand the microstructure was primarily Co metal and a metal-rich silicide phase. The native oxide layer played an important role in minimizing the Co-Si reaction. For laser energy densities E_{2}\geq E_{Si}, spatially ordered patterns with periodic length scales L<Λwere observed and resulted from interference of an incident laser beam with a beam transmitted into the Si substrate. These nanopatterns showed one- as well as two-dimensional spatial ordering of the nanostructures. The microstructure in this laser energy regime was dominated by silicide formation. These results suggest that various nanostructures and microstructures, ranging from nearly pure metal to a Si-rich silicide phase can be formed by appropriate choice of the laser energy simultaneous with film growth.

cond-mat.mtrl-sci↗