E2 transitions and quadrupole moments in the E(5) symmetry

E2 transitions and quadrupole moments are studied in the recently proposed E~5! symmetry by using the intrinsic state formalism. It is shown that the values of these magnitudes can be obtained for the different bands to higher order in the boson number N by projecting the intrinsic state on g and b variables. The formalism allows to find easily the dependence of those magnitudes on the structure parameter of the quadrupole operator, x.Dirección General de Investigación Científica y Técnica PB98-111

Search for critical-point nuclei in terms of the sextic oscillator

The spherical to deformed γ-unstable shape transition in nuclei is discussed in terms of the sextic oscillator as a γ-independent potential in the Bohr Hamiltonian. The wave functions, energy eigenvalues, and electric quadrupole and monopole transition rates are calculated in closed analytical form for the lowest-lying energy levels. It is shown that the locus of critical points for the spherical to deformed γ-unstable shape phase transition corresponds to a parabola in the parameter space of the model. The ratios of energy eigenvalues and electromagnetic transition probabilities are constant along this parabola. It is thus possible to associate parameter-free benchmark values to the ratios of relevant observables at the critical point of the transition that can be compared to experimental data. In addition, systematic studies of the shape evolution in isotope chains can be performed within the model. As an application, the model parameters are fitted to the energy spectra of the chains of even-even Ru, Pd, and Cd isotopes and the electric quadrupole transition probabilities are calculated. It is found that 104Ru, 102Pd, and 106, 108Cd nuclei, which are usually considered to be good candidates for the E(5) symmetry, lie rather close to the critical parabola that separates the spherical and deformed γ-unstable domains. The isotope 116Cd is proposed as a new candidate for a similar critical-point nucleus.FEDER FIS2008-04189MECCPAN-IngenioJunta de Andalucí

A beyond mean field study of Bose gases in a double-well potential with a Feshbach resonance

The Bose-Hubbard model coupled to a Feshbach resonance is studied. Quantum phase transitions are analyzed within a beyond mean field framework in order to get finite size corrections to the simple mean field approach. Analytical results for the ground state energy and the first few energy gaps are presented

Configuration localized Morse wave functions: Application to vibrational transitions in anharmonic diatomic molecules

The bound states of a Morse potential are described in terms of a basis of states that are characterized for being eigenstates of the Morse variable. These states are strongly localized in configuration space; thus they are called configuration localized Morse (CLM) wave functions. These are shown to provide a powerful tool to calculate analytically, to a good approximation, matrix elements of arbitrary functions of the interatomic separation between vibrational states of anharmonic diatomic molecules. Applications of CLM wave functions to the calculation of vibrational transitions in HF and DF diatomic molecules are presented.Dirección General de Investigación Científica y Técnica PB95-0533European Commission CI1*-CT94-007

Analytic evaluation of Franck-Condon integrals for anharmonic vibrational wave functions

The problem of calculating Franck-Condon overlap integrals in molecular transitions between vibrational states in different electronic configurations is addressed. An exact and easily applicable analytical expression is obtained when the vibrational states can be approximated by eigenstates of Morse potentials with different strengths and locations but identical ranges. An approximate analytical expression is obtained for the general case. The method is applied to the stretching S-S mode corresponding to [Formula Presented] transitions in the [Formula Presented] molecule.Dirección General de Investigación Científica y Técnica PB95-053

Core excitation effects in halo nuclei using a transformed oscillator basis

A recent generalization of the Transformed Harmonic Oscillator basis, intended to consider core excitations in the structure of one nucleon halo nuclei, is applied to the break up of 11Be. The reaction studied is 11Be+208Pb at 69 MeV/nucleon. The experimental set up is designed to ensure pure dipole Coulomb excitations. Making use of the Equivalent Photon Method and the electromagnetic transition probabilities obtained with the transformed oscillator basis, a relevant contribution of the quadrupole excitations of the core is found. The inclusion of core excitations is, therefore, necessary for the correct extraction of the dipole electromagnetic transition probability of halo nuclei.Ministerio de Ciencia e Innovación FIS2011-28738-c02-01, FPA2009- 07653, FPA2009-08848, CSD2007-00042Junta de Andalucía FQM160, P07-FQM-0289

Stabilization method in two-body systems with core excitations

The validity of the stabilization method in core+valence systems including the possibility of exciting the core is studied. A pseudostate method, based on the transformed harmonic oscillator basis, is extended to include the core degrees of freedom. The method is applied to the case of 11Be structure considering the 0+ ground state and the 2+ first excited state of the 10Be core. The stabilization method is defined in terms of one parameter that can be chosen either discrete or continuous. In the application to 11Be, both cases are analyzed.Ministerio de Ciencia e Innovación FIS2011-28738-c02-01, FPA2009-07653, FPA2009-08848, CSD2007-00042Junta de Andalucía FQM160, P07-FQM-0289

Number conserving particle-hole RPA for superfluid nuclei

TheAuthor(s) - .Published by Elsevier B.V. "This is an open access article under the CCBY license (http://creativecommons.org/licenses/by/4.0/).Funded by SCOAP"We present a number conserving particle-hole RPA theory for collective excitations in the transition from normal to superfluid nuclei. The method derives from an RPA theory developed long ago in quantum chemistry using antisymmetric geminal powers, or equivalently number projected HFB states, as reference states. We show within a minimal model of pairing plus monopole interactions that the number conserving particle-hole RPA excitations evolve smoothly across the superfluid phase transition close to the exact results, contrary to particle-hole RPA in the normal phase and quasiparticle RPA in the superfluid phase that require a change of basis at the broken symmetry point. The new formalism can be applied in a straightforward manner to study particle-hole excitations on top of a number projected HFB state.Consejería de Economía, Conocimiento, Empresas y Universidad de la Junta de Andalucía (Spain) FQM-160 and FQM-370Fondo Europeo de Desarrollo Regional (ERDF), ref. SOMM17/6105/UGRMinisterio de Ciencia, Innovación y Universidades and the ERDF under Projects No. FIS2015-63770-P, FIS2017-88410-P and PGC2018-094180-B-I00CEAFMC and Universidad de Huelva High Performance Computer (HPC@UHU) funded by FEDER/MINECO project UNHU-15CE-284

Number conserving particle-hole RPA for superfluid nuclei

TheAuthor(s) - .Published by Elsevier B.V. "This is an open access article under the CCBY license (http://creativecommons.org/licenses/by/4.0/).Funded by SCOAP"We present a number conserving particle-hole RPA theory for collective excitations in the transition from normal to superfluid nuclei. The method derives from an RPA theory developed long ago in quantum chemistry using antisymmetric geminal powers, or equivalently number projected HFB states, as reference states. We show within a minimal model of pairing plus monopole interactions that the number conserving particle-hole RPA excitations evolve smoothly across the superfluid phase transition close to the exact results, contrary to particle-hole RPA in the normal phase and quasiparticle RPA in the superfluid phase that require a change of basis at the broken symmetry point. The new formalism can be applied in a straightforward manner to study particle-hole excitations on top of a number projected HFB state.Consejería de Economía, Conocimiento, Empresas y Universidad de la Junta de Andalucía (Spain) FQM-160 and FQM-370Fondo Europeo de Desarrollo Regional (ERDF), ref. SOMM17/6105/UGRMinisterio de Ciencia, Innovación y Universidades and the ERDF under Projects No. FIS2015-63770-P, FIS2017-88410-P and PGC2018-094180-B-I00CEAFMC and Universidad de Huelva High Performance Computer (HPC@UHU) funded by FEDER/MINECO project UNHU-15CE-284

Connection between decoherence and excited state quantum phase transitions

In this work we explore the relationship between an excited state quantum phase transition (ESQPT) and the phenomenon of quantum decoherence. For this purpose, we study how the decoherence is affected by the presence of a continuous ESQPT in the environment. This one is modeled as a two level boson system described by a Lipkin Hamiltonian. We will show that the decoherence of the system is maximal when the environment undergoes a continuous ESQPT