98 research outputs found
Epitaxial EuO Thin Films on GaAs
We demonstrate the epitaxial growth of EuO on GaAs by reactive molecular beam
epitaxy. Thin films are grown in an adsorption-controlled regime with the aid
of an MgO diffusion barrier. Despite the large lattice mismatch, it is shown
that EuO grows well on MgO(001) with excellent magnetic properties. Epitaxy on
GaAs is cube-on-cube and longitudinal magneto-optic Kerr effect measurements
demonstrate a large Kerr rotation of 0.57{\deg}, a significant remanent
magnetization, and a Curie temperature of 69 K.Comment: 5 pages, 3 figure
Identification of medium mass (A=60-80) ejectiles from 15 MeV/nucleon peripheral heavy-ion collisions with the MAGNEX large-acceptance spectrometer
An approach to identify medium-mass ejectiles from peripheral heavy-ion
reactions in the energy region of 15 MeV/nucleon is developed for data obtained
with a large acceptance magnetic spectrometer. This spectrometer is equipped
with a focal plane multidetector, providing position, angle, energy loss and
residual energy of the ions along with measurement of the time-of-flight. Ion
trajectory reconstruction is performed at high order and ion mass is obtained
with a resolution of better than 1/150. For the unambiguous particle
identification however, the reconstruction of both the atomic number Z and the
ionic charge q of the ions is critical and it is suggested, within this work,
to be performed prior to mass identification. The new proposed method was
successfully applied to MAGNEX spectrometer data, for identifying neutron-rich
ejectiles related to multinucleon transfer generated in the 70Zn+ 64Ni
collision at 15 MeV/nucleon. This approach opens up the possibility of
employing heavy-ion reactions with medium-mass beams below the Fermi energy
(i.e., in the region 15-25 MeV/nucleon) in conjunction with large acceptance
ray tracing spectrometers, first, to study the mechanism(s) of nucleon transfer
in these reactions and, second, to produce and study very neutron-rich or even
new nuclides in previously unexplored regions of the nuclear landscape.Comment: 6 pages, 6figure
One-neutron transfer reaction in the O + Ti collision at 275 MeV
The present article reports new data on the
Ti(O,O)Ti reaction at 275 MeV incident energy as
part of the systematic research pursued within the NUMEN project. Supplementary
measurements of the same reaction on O and Al targets were also
performed in order to estimate the background arising from the use of a
composite target (TiO + Al). These data were analyzed under the
same theoretical framework as those obtained with the titanium target in order
to reinforce the conclusions of our analysis. Differential cross-section
angular distribution measurements for the O ejectiles were
performed in a wide angular range by using the MAGNEX large acceptance magnetic
spectrometer. The experimental results were analyzed within the distorted-wave
and coupled-channels Born Approximation frameworks. The optical potentials at
the entrance and exit channels were calculated in a double folding approach
adopting the S\~ao Paulo potential, and the spectroscopic amplitudes for the
projectile and target overlaps were obtained from large-scale shell model
calculations. The differential cross-sections are well-described by the
theoretical calculations, where a weak coupling to collective excitations of
projectile and target is inferred. The sensitivity of transfer cross-sections
on different model spaces adopted in nuclear structure calculations, is also
discussed
One-proton transfer reaction for the O 18 + Ti 48 system at 275 MeV
Single-nucleon transfer reactions are processes that selectively probe single-particle components of the populated many-body nuclear states. In this context, recent efforts have been made to build a unified description of the rich nuclear spectroscopy accessible in heavy-ion collisions. An example of this multichannel approach is the study of the competition between successive nucleon transfer and charge exchange reactions, the latter being of particular interest in the context of single and double beta decay studies. To this extent, the one-proton pickup reaction Ti48(O18,F19)Sc47 at 275 MeV was measured for the first time, under the NUMEN experimental campaign. Differential cross-section angular distribution measurements for the F19 ejectiles were performed at INFN-LNS in Catania by using the MAGNEX large acceptance magnetic spectrometer. The data were analyzed within the distorted-wave and coupled-channels Born approximation frameworks. The initial and final-state interactions were described adopting the SĂŁo Paulo potential, whereas the spectroscopic amplitudes for the projectile and target overlaps were derived from shell-model calculations. The theoretical cross sections are found to be in very good agreement with the experimental data, suggesting the validity of the optical potentials and the shell-model description of the involved nuclear states within the adopted model space
A constrained analysis of the 40Ca(18O,18F)40K direct charge exchange reaction mechanism at 275 Mev
The40 Ca(18 O,18 F)40 K single charge exchange (SCE) reaction is explored at an incident energy of 275 MeV and analyzed consistently by collecting the elastic scattering and inelastic scattering data under the same experimental conditions. Full quantum-mechanical SCE calculations of the direct mechanism are performed by including microscopic nuclear structure inputs and adopting either a bare optical potential or a coupled channel equivalent polarization potential (CCEP) constrained by the elastic and inelastic data. The direct SCE mechanism describes the magnitude and shape of the angular distributions rather well, thus suggesting the suppression of sequential multi-nucleon transfer processes
Background estimate in heavy-ion two-body reactions measured by the MAGNEX spectrometer
The MAGNEX magnetic spectrometer is nowadays used in the experimental measurements of rare quasi-elastic reactions between heavy ions at intermediate energy within the NUMEN project. The small cross sections involved in such processes under the large yields due to competitive reaction channels have motivated an accurate control of the background sources. In such view, the not ideal particle identification could introduce spurious contributions which have been identified and evaluated in the present analysis
The NUMEN heavy ion multidetector for a complementary approach to the neutrinoless double beta decay
Neutrinos are so far the most elusive known particles, and in the last decades many sophisticated experiments have been set up in order to clarify several questions about their intrinsic nature, in particular their masses, mass hierarchy, intrinsic nature of Majorana or Dirac particles. Evidence of the Neutrinoless Double-Beta Decay (NDBD) would prove that neutrinos are Majorana particles, thus improving the understanding of the universe itself. Besides the search for several large underground experiments for the direct experimental detection of NDBD, the NUMEN experiment proposes the investigation of a nuclear mechanism strongly linked to this decay: the Double Charge Exchange reactions (DCE). As such reactions share with the NDBD the same initial and final nuclear states, they could shed light on the determination of the Nuclear Matrix Elements (NMEs), which play a relevant role in the decay. The physics of DCE is described elsewhere in this issue, while the focus of this paper will be on the challenging experimental apparatus currently under construction in order to fulfil the requirements of the NUMEN experiment. The overall structure of the technological improvement to the cyclotron, along with the newly developed detection systems required for tracking and identifying the reaction products and their final excitation level are described
Recent results on Heavy-Ion induced reactions of interest for 0νββ decay
An updated overview of recent results on Heavy-Ion induced reactions of interest for neutrinoless double beta decay is reported in the framework of the NUMEN project. The NUMEN idea is to study heavy-ion induced Double Charge Exchange (DCE) reactions with the aim to get information on the nuclear matrix elements for neutrinoless double beta (0νββ) decay. Moreover, to infer the neutrino average masses from the possible measurement of the half- life of 0νββ decay, the knowledge of the nuclear matrix elements is a crucial aspec
The NUMEN heavy ion multidetector for a complementary approach to the neutrinoless double beta decay
Neutrinos are so far the most elusive known particles, and in the last decades many sophisticated experiments have been set up in order to clarify several questions about their intrinsic nature, in particular their masses, mass hierarchy, intrinsic nature of Majorana or Dirac particles. Evidence of the Neutrinoless Double-Beta Decay (NDBD) would prove that neutrinos are Majorana particles, thus improving the understanding of the universe itself. Besides the search for several large underground experiments for the direct experimental detection of NDBD, the NUMEN experiment proposes the investigation of a nuclear mechanism strongly linked to this decay: the Double Charge Exchange reactions (DCE). As such reactions share with the NDBD the same initial and final nuclear states, they could shed light on the determination of the Nuclear Matrix Elements (NMEs), which play a relevant role in the decay. The physics of DCE is described elsewhere in this issue, while the focus of this paper will be on the challenging experimental apparatus currently under construction in order to fulfil the requirements of the NUMEN experiment. The overall structure of the technological improvement to the cyclotron, along with the newly developed detection systems required for tracking and identifying the reaction products and their final excitation level are described
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