Time filter

Source Type

Rome, Italy

Hatada K.,University of Zaragoza | Hatada K.,National Institute of Nuclear Physics, Italy | Hayakawa K.,National Institute of Nuclear Physics, Italy | Hayakawa K.,Centro Fermi | Palumbo F.,National Institute of Nuclear Physics, Italy
Physical Review C - Nuclear Physics | Year: 2011

Scissors modes were predicted in the framework of the two-rotor model. This model has an intrinsic harmonic spectrum, so that the level above the scissors mode, the first overtone, has excitation energy twice that of the scissors mode. Because the latter is of the order of 3 MeV in the rare-earth region, the energy of the overtone is below threshold for nucleon emission, and its width should remain small enough for the overtone to be observable. We find that B(E2)'overtone=164θ02B(E2)'scissors, where θ0 is the zero-point oscillation amplitude, which in the rare-earth region is of order 10-1. © 2011 American Physical Society.

Chiappini A.,CNR Institute for Photonics and Nanotechnologies | Armellini C.,CNR Institute for Photonics and Nanotechnologies | Carpentiero A.,CNR Institute for Photonics and Nanotechnologies | Minati L.,CNR Institute for Photonics and Nanotechnologies | And 3 more authors.
Optical Materials | Year: 2013

In this paper we describe a composite system based on polystyrene colloidal nanoparticles assembled and embedded in an elastomeric matrix (polymer colloidal crystal, PCC), in the specific we have designed a PCC structure which displays an iridescent green color that can be attributed to the photonic crystal effect. This effect has been exploited to create a chemical sensor, in fact optical measurements have evidenced that the composite structure presents a different optical response as a function of the solvent applied on the surface. In particular we have demonstrated that the PCC possess, for specific solvents: (i) high sensitivity, (ii) fast response (less than 1s), and (iii) reversibility of the signal change. Finally preliminary results on the PCC have shown that this system can be also used as optical writing substrate using a specific solvent as ink, moreover an erasing procedure is also reported and discussed. © 2013 Elsevier B.V. All rights reserved.

Hatada K.,University of Zaragoza | Hatada K.,National Institute of Nuclear Physics, Italy | Hayakawa K.,National Institute of Nuclear Physics, Italy | Hayakawa K.,Centro Fermi | And 3 more authors.
Journal of Physics Condensed Matter | Year: 2010

We present a rigorous derivation of a real-space full-potential multiple scattering theory (FP-MST) that is free from the drawbacks that up to now have impaired its development (in particular the need to expand cell shape functions in spherical harmonics and rectangular matrices), valid both for continuum and bound states, under conditions for space partitioning that are not excessively restrictive and easily implemented. In this connection we give a new scheme to generate local basis functions for the truncated potential cells that is simple, fast, efficient, valid for any shape of the cell and reduces to the minimum the number of spherical harmonics in the expansion of the scattering wavefunction. The method also avoids the need for saturating 'internal sums' due to the re-expansion of the spherical Hankel functions around another point in space (usually another cell center). Thus this approach provides a straightforward extension of MST in the muffin-tin (MT) approximation, with only one truncation parameter given by the classical relation lmax = kRb, where k is the electron wavevector (either in the excited or ground state of the system under consideration) and Rb is the radius of the bounding sphere of the scattering cell. Moreover, the scattering path operator of the theory can be found in terms of an absolutely convergent procedure in the limit. Consequently, this feature provides a firm ground for the use of FP-MST as a viable method for electronic structure calculations and makes possible the computation of x-ray spectroscopies, notably photo-electron diffraction, absorption and anomalous scattering among others, with the ease and versatility of the corresponding MT theory. Some numerical applications of the theory are presented, both for continuum and bound states. © 2010 IOP Publishing Ltd.

Frezzotti R.,University of Rome Tor Vergata | Rossi G.C.,University of Rome Tor Vergata | Rossi G.C.,Centro Fermi
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

Taking inspiration from lattice QCD data, we argue that a finite nonperturbative contribution to the quark mass is generated as a consequence of the dynamical phenomenon of spontaneous chiral symmetry breaking, in turn triggered by the explicit breaking of chiral symmetry induced by the critical Wilson term in the action. In pure lattice QCD this mass term cannot be separated from the unavoidably associated linearly divergent contribution. However, if QCD is enlarged to a theory where also a scalar field is present, coupled to an SU(2) doublet of fermions via a Yukawa and a Wilson-like term, then in the phase where the scalar field takes a nonvanishing expectation value, a dynamically generated and "naturally" light fermion mass (numerically unrelated to the expectation value of the scalar field) is conjectured to emerge at a critical value of the Yukawa coupling where the symmetry of the model is maximally enhanced. Masses dynamically generated in this way display a natural hierarchy according to which the stronger is the strongest of the interactions the fermion is subjected to, the larger will be its mass. © 2015 American Physical Society. © 2015 American Physical Society.

Hatada K.,University of Zaragoza | Hatada K.,National Institute of Nuclear Physics, Italy | Hayakawa K.,National Institute of Nuclear Physics, Italy | Hayakawa K.,Centro Fermi | Palumbo F.,National Institute of Nuclear Physics, Italy
European Physical Journal B | Year: 2010

We recently suggested that the Scissors Mode (a collective excitation in which one system rotates with respect another one conserving its shape) can occur in crystals with axially symmetric atoms as a precession of these atoms around the anisotropy axis of their cells, giving rise to a form of dichroism. In the present paper we investigate how the Scissors Mode can be realized in crystals with cubic symmetry and evaluate its photo-absorption cross-section. This turns out to be of the same order of magnitude as that for crystals with axially symmetric atoms, but does not exhibit any correlation between the direction of the photon and the axes of the cell. © EDP Sciences, Societa Italiana di Fisica, Springer-Verlag 2010.

Discover hidden collaborations