Repositório RCAAP

Franck-Condon factors (vibrational transition probabilities) and r-centroids have been evaluated by a numerical integration procedure for the bands of A 0+g - X ¹sigma+, B 0+g - X ¹sigma+ systems of AuH and A 0+ - X ¹sigma+ system of AuD molecules using a suitable potential. The physical and astrophysical significances of our evaluated Franck-Condon factors and r-centroids have also been discussed, which would be helpful in the prediction of the presence of AuH and AuD molecules in various celestial bodies.

The Symplectic Projector Method is applied to derive the local physical degrees of freedom and the physical Hamiltonian of the Maxwell-Chern-Simons theory in d = 1+2. The results agree with the ones obtained in the literature through different approaches.

This paper is devoted to a review of recent progresses concerning the computation of the Casimir force between two parallel plates delimitating a polymer blend or a ternary polymer solution (with a good solvent). We assume that, close to the consolute point, one or the two polymers of the mixture are strongly attracted by the plates (critical adsorption). For both systems, the induced force originates from the fluctuations of composition near the consolute point. In polymer blends case, it was found that the force decreases with separation L between the two plates as L-4, with a known universal amplitude. For ternary polymer solutions, however, it has been shown that the interaction force decays rather as L-3. This drastic change of the force expression is due to the presence of the good solvent, which gives rise to additional fluctuations of polymer concentration. To do calculations, for the two systems, use is made of the standard sigma4-theory, where the field sigma is the order parameter or composition fluctuation.

This paper is the outgrowth of lectures the author gave at the Physics Institute and the Chemistry Institute of the University of São Paulo at São Carlos, Brazil, and at the VIII'th Summer School on Electronic Structure of the Brazilian Physical Society. It is an attempt to introduce density-functional theory (DFT) in a language accessible for students entering the field or researchers from other fields. It is not meant to be a scholarly review of DFT, but rather an informal guide to its conceptual basis and some recent developments and advances. The Hohenberg-Kohn theorem and the Kohn-Sham equations are discussed in some detail. Approximate density functionals, selected aspects of applications of DFT, and a variety of extensions of standard DFT are also discussed, albeit in less detail. Throughout it is attempted to provide a balanced treatment of aspects that are relevant for chemistry and aspects relevant for physics, but with a strong bias towards conceptual foundations. The paper is intended to be read before (or in parallel with) one of the many excellent more technical reviews available in the literature.

The accumulation and distribution of 40K and 137Cs in tropical plant species were studied through measurements of gamma-ray spectra from mango, avocado, guava, pomegranate, chili pepper, papaya and manioc trees. Our goal was to infer their differences in the uptake and translocation of ions to the aboveground plant parts and to establish the suitability of using radiocaesium as a tracer for the plant uptake of nutrients such as K+.

In this work we perform quasiparticle-rotor coupling model calculations within the usual BCS and the projected BCS for the carbon isotopes 15C, 17C and 19C using 13C as the building block. Owing to the pairing correlation, we find that 13C as well as the cores of the other isotopes, namely 14C, 16C and 18C acquire strong and varied deformations. The deformation parameter is large and negative for 12C, very small (or zero) for 14C and large and positive for 16C and 18C. This finding casts a doubt about the purity of the supposed simple one-neutron halo nature of 19C.

In this work, a model based on single particle plus pairing residual interaction was used to study the low-lying excited states of the 193Ir nucleus. In this model, the deformation parameters in equilibrium were obtained by minimizing the total energy calculated by the Strutinsky prescription; the macroscopic contribution to the potential was taken from the Liquid Droplet Model, with the shell and paring corrections used as as microscopic contributions. The nuclear shape was described using the Cassinian ovoids as base figures; the single particle energy spectra and wave functions for protons and neutrons were calculated in a deformed Woods-Saxon potential, where the parameters for neutrons were obtained from the literature and the parameters for protons were adjusted in order to describe the main sequence of angular momentum and parity of the bandheads, as well as the proton binding energy of 193Ir. The residual pairing interaction was calculated using the BCS prescription with Lipkin-Nogami approximation. The results obtained for the first three bandheads (the 3/2+ ground state, the 1/2+ excited state at E ~ 73keV and the the 11/2- isomeric state at E ~ 80keV) showed a very good agreement, but the model so far greatly overestimated the energy of the next bandhead, a 7/2- at E ~ 299keV.

We present general explicit expressions for a shell-model calculationof the vector hypernuclear parameter in nonmesonic weak decay. We use a widely accepted effective coupling Hamiltonian involving theexchange of the complete pseudoscalar and vector meson octets(<FONT FACE=Symbol>p, h</FONT>, K, <FONT FACE=Symbol>r, w</FONT>, K*). In contrast to the approximated formula widely used in the literature,we correctly treat the contribution of transitions originated fromsingle-proton states beyond the s-shell. Exact and simple analytical expressions are obtained for the particularcases of $^5_Lambda$He and $^{12}_\Lambda$C, within theone-pion-exchange model. Numerical computations of the asymmetry parameter, $a_\Lambda$, are presented. Our results show a qualitative agreementwith other theoretical estimates but also acontradiction with recent experimental determinations. Our simple analytical formulas provide a guide in searchingthe origin of such discrepancies, andthey will be useful for helping to solve the hypernuclearweak decay puzzle.

Low-lying levels of 103Pd have been investigated through the (d,t) reaction on 104Pd, at an incident deuteron energy of 15.0 MeV. Outgoing particles were momentum analyzed by an Enge magnetic spectrograph and detected in nuclear emulsion plates, with an energy resolution of 8 keV. Previous (d,t) work suffered from a much worse resolution than that here achieved. A partial analysis of the data obtained is reported, referring to six out of the fourteen scattering angles for which data were obtained. Angular distributions associated with eight of the thirteen levels seen up to 1.1 MeV of excitation have been compared to DWBA one-neutron pick-up predictions. Both, the attributed excitation energy values and the transferred angular momenta are in excellent agreement with the results of other kind of experiments, as tabulated by the Nuclear Data Sheets. Some peculiar structure characteristics, associated with the yrast 5/2+, 3/2+ and 7/2+ states found in the Ru chain could be recognized also in 103Pd, pointing to the possibility of a more global understanding of this transitional mass region.

The in-medium influence on pi0 photoproduction from spin zero nuclei is carefully studied in the GeV range using a straightforward Monte Carlo analysis. The calculation takes into account the relativistic nuclear recoil for coherent mechanisms (electromagnetic and nuclear amplitudes) plus a time dependent multi-collisional intranuclear cascade approach (MCMC) to describe the transport properties of mesons produced in the surroundings of the nucleon. A detailed analysis of the meson energy spectra for the photoproduction on 12C at 5.5 GeV indicates that both the Coulomb and nuclear coherent events are associated with a small energy transfer to the nucleus ($\lesssim$ 5 MeV), while the contribution of the nuclear incoherent mechanism is vanishing small within this kinematical range. The angular distributions are dominated by the Primakoff peak at extreme forward angles, with the nuclear incoherent process being the most important contribution above $\theta_{\pi^{0}}\gtrsim2^{0}$. Such consistent Monte Carlo approach provides a suitable method to clean up nuclear backgrounds in some recent high precision experiments, such as the PrimEx experiment at the Jefferson Laboratory Facility.

High-spin states in the neutron-deficient140Gd nucleus have been studied with the 92Mo(54Fe,alpha2p) reaction at a beam energy of 240 MeV. The level scheme of 140Gd was considerably extended from what was previously known. In this work we concentrate on one of the 9 bands observed, which presents relatively strong M1 transitions and negligible signature splitting, and has an isomeric band-head, indicating a strongly coupled or high-K configuration. We compare this band to the Kpi = 8- bands observed in N=74 isotones and propose a similar configuration assignment, but with a somewhat larger deformation.

We use the Peierls-Yoccoz projection method to evaluate the center-of-mass correction of a relativistic system of nucleons and sigma and omega mesons, described in a mean-field Hartree approach. This correction for 4He, 16O and 40Ca is compared with the pure harmonic oscillator center-of-mass energy correction.

We compare the cross sections for Coulomb excitation of multiple giant dipole resonances in 208Pb + 208Pb scattering using Coulomb trajectories and straight-line trajectories that have the same point of closest approach as the Coulomb one. We find the effects of the Coulomb deflection relative to the straight line trajectory to be small at incident energies above about 500 MeV/nucleon.

Nuclear fissilities obtained from recent photofission reaction cross section measurements carried out at Saskatchewan Accelerator Laboratory (Saskatoon, Canada) in the energy range 60-130 MeV for 232Th, 233U, 235U, 238U, and 237Np nuclei have been analysed in a systematic way. To this aim, a semiempirical approach has been developed based on the quasi-deuteron nuclear photoabsorption model followed by the process of competition between neutron evaporation and fission for the excited nucleus. The study reproduces satisfactorily well the increasing trend of nuclear fissility with parameter Z²/A.

The purpose of this work is to correlate Sr/Ca ratio with internal body temperature from teeth and bones. Results obtained in exploratory measurements using human, bovine and swine teeth indicated some relation between temperature and Sr/Ca ratio, but no other parameters, as feeding habits that certainly has some influence over Sr/Ca ratio, were controlled. In this work, to eliminate feeding effects, we decided to compare Sr/Ca ratio of bones from some individual. The first bones irradiated were from a crocodile (Caiman Yacare), which regulates the internal body temperature by the temperature of its surroundings. The pieces irradiated were from the crocodile's tail, vertebral column and leg. To quantify Sr and Ca a 2.4 MeV proton beam was used in PIXE beam line at LAMFI - USP. Emitted X-rays were collected using a Si(Li) detector (150eV @ 6.4 KeV). First results show that the bones closer to the heart have a lower Sr/Ca ratio.

Recent results obtained in the Chromodielectric Model (CDM) have shown that strange quark matter at very high densities may appear in two phases, namely a chiral broken and a chiral symmetric phase, which may not be absolutely stable. In the chiral symmetric phase, the abundance of the quarks flavors u, d and s is the same and there are no electrons. In this paper we study an extended version of the Chromodielectric model (CDM) with a BCS quark pairing implemented, and analyze the superconducting color flavor locked phase. We show that the inclusion in the free energy density of a negative term of the diquark condensate guarantees the stability of quark matter. We also analyze the phase transition between matter described by different equations of state and only find a first order transition, at a very low pressure, from the CFL phase to the unpaired strange quark matter, which opens the possibility for a quark-hadron phase transition. Our study has implications in astrophysics, in particular regarding the formation and the structure of compact quark stars. We explicitly show that CFL stars can be absolutely stable and more compact than strange stars.

We review the existing mass and decay width determinations of pentaquarks with QCD Sum Rules (QCDSR). We give special attention to the intermediate assumptions and choices which we are obliged to do in this approach. As an example, we present the full calculation of the pentaquark mass with Borel sum rules and also with Finite Energy Sum Rules (FESR). We also work out the calculation of the theta decay width. We take the opportunity to comment our publications on this subject and include new and unpublished material.

In this article we write a biographical note about Yogiro Hama. It is quite an amazing life story, as you will read in the pages below. In the second part of this article we include many messages and letters sent by several of his friends and collaborators for the celebration of his 70th birthday.

As part of the celebration of his 70th birthday, I review the works done in collaboration with Prof. Yogiro Hama and try to recover the history of some of his ideas concerning the formation of a fluid in high energy hadronic collisions, its expansion and dissociation. I show how these ideas evolved and how they are relevant for understanding the present experimental data.

I present a brief overview on the motivation for performing relativistic nuclear collisions and the justification for using hydrodynamics to describe them. The contribution of Prof. Hama to the field of hydrodynamics and his efforts to form a group working on this subject are outlined.