ANNUAL REPORT 2011 - Instituto de Estructura de la Materia

We have studied the bulk and spectroscopic properties of neutron-rich even-even and odd-A isotopes in this massregion within the selfconsistent Hartree-Fock-Bogoliubov approximation based on the finite range and densitydependent Gogny energy density functional (EDF). In addition to the well known D1S parametrization of theGogny-EDF, we also consider the most recent parametrization D1M. From this comparison we evaluate not only therobustness of our results, but we also explore the capability of D1M to account for the phenomenology of odd-Anuclei, not so well studied yet. The description of the odd-A nuclei is done in terms of the equal fillingapproximation, a prescription widely used in mean-field calculations to preserve the advantages of time-reversalinvariance. We have analyzed various nuclear properties, such as two-neutron separation energies, charge radii, andthe spin-parity of ground states in a search for signatures of shape transitions. In several isotopic chains we havefound clear signatures of a sharp shape transition at N=60 in both charge radii and spin-parity of the ground states,which are robust, consistent to each other, and in agreement with experiment. In other isotopic chains the shapetransition disappears, stabilizing one of the shapes or developing triaxial deformations. We point out that thecombined analysis of these two observables could be used to predict unambiguously new regions where shapetransitions might develop.THEORETICAL PHYSICAL-CHEMISTRY APPLIED TO ASTROPHYSICSDuring 2011, we have performed molecular studies within the three sub-lines of research carried out by our group:molecular spectroscopy of prebiotic non-rigid molecules of astrophysical interest; structural and spectroscopiccharacterization of semi-rigid species of astrophysics and atmospheric importance and determination of crosssections in non reactive inelastic collisions at very low temperatures. In all these works, high-level ab initiocalculations are used as a basic tool to determine potential energy surfaces and molecular structures. From thesemethods and with our ro-vibracional codes ENEDIM and FIT-SPEC we predicted many spectroscopic properties.Molecules and the problems addressed are relevant to the study of the gas phase chemistry of the interstellar andcircunestelar media and planetary atmospheres. Research carried out within the scientific exploitation of newobservatories Herschel and ALMA programs.In recent years, we have been developing very detailed studies focused to the characterization of carbon-chains ofastrophysical importance. Carbon-chains are relevant isolated species as well as important intermediates offormation processes of large molecules such as the PAHs and Fullerenes. We have studied with very precisemethods small size chains that are relatively abundant in carbon rich sources. We initiated the sequence by purechains type C n with a reduced number of atoms (n) and likely to be detected with infrared techniques using theinstruments of the new Herschel Space Observatory. Currently, we are studying neutral and charged chains typeC n X m (X = Si, S or H) and type SiNH n . These species, which are difficult to be treated at the laboratory level for itslow stability, have permanent dipole moment and are therefore detectable through radio astronomy. They aretherefore relevant species with a view to the future project ALMA. We provided special attention to the anions dueto the recent interest awaken in the astrophysical community, studying C 4 H - (detected by IEM astronomers) andanions type SiC n and SiC n H. We have identified isomeric structures, potential energy surfaces for the first electronicstates, as well as rovibrational properties including anharmonicity effects. We provide possible isomerizationprocesses and predict Renner-Teller and rovibronic effects.For the ALMA project science exploitation, it is necessary to understand the millimeter and sub-millimeter spectraof non-rigid molecules containing the most abundant interstellar elements C, N, O and H. Many of these moleculesare classified as prebiotic. They show very low energy vibrational levels that can be populated at very lowtemperatures. These levels correspond to the large amplitude vibrations that inter-transform minimum energystructures through feasible potential energy barriers. Given the astrophysical interest, we are studying with veryprecise initio method the torsional and bending modes of dimethyl-ether and methyl format. Recently, UREA has53