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2012
Guimarães, Diana, Maria Luisa Carvalho, Vera Geraldes, Isabel Rocha, Luís Cerqueira Alves, and Jose Paulo Santos. "Lead in liver and kidney of exposed rats: Aging accumulation study." Journal of Trace Elements in Medicine and Biology 26 (2012): 285. AbstractWebsite

The concentration of lead in liver and kidneys of Wistar rats, fed with lead since fetal period in relation to their age and to a control group, was determined. A group of rats was exposed to lead acetate (n=30) in drinking water and the other group was exposed to normal water (n=20). Samples were collected from rats aging between 1 and 11 months and were analyzed by Energy Dispersive X-ray Fluorescence (EDXRF) without any chemical preparation. The EDXRF results were assessed by the PIXE (Proton Induced X-ray Emission) technique. The formaldehyde used to preserve the samples was also analyzed by ETAAS (Electro-Thermal Atomic Absorption Spectrometry) in order to verify if there was any loss of lead from the samples to the formaldehyde. We found that the loss was not significant (<2%). Concerning the mean values of the lead concentration measured in the contaminated soft tissues, in liver they range from 6 to 22μgg(-1), and in kidneys from 44 to 79μgg(-1). The control rats show, in general, values below the EDXRF detection limit (2μgg(-1)). The ratio kidney/liver ranges from 2 to 10 and is strongly positively correlated with the age of the animals. A Spearman correlation matrix to investigate the correlation between elemental concentrations and the dependence of these concentrations with age showed that there is a strong positive correlation with age for lead in the liver but not in the kidney. The correlation matrix showed also that the concentration of lead in these two soft tissues is not correlated. The lead accumulation in liver is made by different plateaus that strongly decrease with age. It was verified the existence of two levels of accumulation in kidney, not very highlighted, which might be indicative of a maximum accumulation level for lead in kidney.

Amaro, P., F. Fratini, S. Fritzsche, P. Indelicato, J. P. Santos, and A. Surzhykov. "Parametrization of the angular correlation and degree of linear polarization in two-photon decays of hydrogenlike ions." Phys. Rev. A 86 (2012): 042509. AbstractWebsite

The spontaneous two-photon emission in hydrogenlike ions is investigated within the framework of second- order perturbation theory and Dirac’s equation. Special attention is paid to the angular correlation of the emitted photons as well as to the degree of linear polarization of one of the two photons, if the second is just observed under arbitrary angles. Expressions for the angular correlation and the degree of linear polarization are expanded in powers of cosine functions of the two-photon opening angle, whose coefficients depend on the atomic number and the energy sharing of the emitted photons. The effects of including higher (electric and magnetic) multipoles upon the emitted photon pairs beyond the electric-dipole approximation are also discussed. Calculations of the coefficients are performed for the transitions 2s1/2 → 1s1/2, 3d3/2 → 1s1/2, and 3d5/2 → 1s1/2, along the entire hydrogen isoelectronic sequence (1

Amaro, P., F. Fratini, S. Fritzsche, P. Indelicato, J. P. Santos, and A. Surzhykov. "Parametrization of the angular correlation and degree of linear polarization in two-photon decays of hydrogenlike ions." Physical Review A 86 (2012): 042509. AbstractWebsite

The spontaneous two-photon emission in hydrogenlike ions is investigated within the framework of second- order perturbation theory and Dirac’s equation. Special attention is paid to the angular correlation of the emitted photons as well as to the degree of linear polarization of one of the two photons, if the second is just observed under arbitrary angles. Expressions for the angular correlation and the degree of linear polarization are expanded in powers of cosine functions of the two-photon opening angle, whose coefficients depend on the atomic number and the energy sharing of the emitted photons. The effects of including higher (electric and magnetic) multipoles upon the emitted photon pairs beyond the electric-dipole approximation are also discussed. Calculations of the coefficients are performed for the transitions 2s1/2 → 1s1/2, 3d3/2 → 1s1/2, and 3d5/2 → 1s1/2, along the entire hydrogen isoelectronic sequence (1 Z 100).

Safari, L., P. Amaro, S. Fritzsche, J. P. Santos, S. Tashenov, and F. Fratini. "Relativistic polarization analysis of Rayleigh scattering by atomic hydrogen." Phys. Rev. A 86 (2012): 043405. AbstractWebsite

A relativistic analysis of the polarization properties of light elastically scattered by atomic hydrogen is performed, based on the Dirac equation and second-order perturbation theory. The relativistic atomic states used for the calculations are obtained by making use of the finite basis set method and are expressed in terms of B splines and B polynomials. We introduce two experimental scenarios in which the light is circularly and linearly polarized, respectively. For each of these scenarios, the polarization-dependent angular distribution and the degrees of circular and linear polarization of the scattered light are investigated as a function of scattering angle and photon energy. Analytical expressions are derived for the polarization-dependent angular distribution which can be used for scattering by both hydrogenic as well as many-electron systems. Detailed computations are performed for Rayleigh scattering by atomic hydrogen within the incident photon energy range 0.5 to 5 keV. Particular attention is paid to the effects that arise from higher (nondipole) terms in the expansion of the electron-photon interaction.

Safari, L., P. Amaro, S. Fritzsche, J. P. Santos, S. Tashenov, and F. Fratini. "Relativistic polarization analysis of Rayleigh scattering by atomic hydrogen." Physical Review A 86 (2012): 043405. AbstractWebsite

A relativistic analysis of the polarization properties of light elastically scattered by atomic hydrogen is performed, based on the Dirac equation and second-order perturbation theory. The relativistic atomic states used for the calculations are obtained by making use of the finite basis set method and are expressed in terms of B splines and B polynomials. We introduce two experimental scenarios in which the light is circularly and linearly polarized, respectively. For each of these scenarios, the polarization-dependent angular distribution and the degrees of circular and linear polarization of the scattered light are investigated as a function of scattering angle and photon energy. Analytical expressions are derived for the polarization-dependent angular distribution which can be used for scattering by both hydrogenic as well as many-electron systems. Detailed computations are performed for Rayleigh scattering by atomic hydrogen within the incident photon energy range 0.5 to 5 keV. Particular attention is paid to the effects that arise from higher (nondipole) terms in the expansion of the electron-photon interaction.

Santos, J. P., A. M. Costa, M. C. Martins, P. Indelicato, and F. Parente. "K X-Ray Energies and Transition Probabilities for He-, Li- and Be-like Praseodymium ions." J. Phys.: Conf. Ser. 388 (2012): 152018. AbstractWebsite

Theoretical transition energies and probabilities for He-, Li and Be-like Praseodymium ions are calcu- lated in the framework of the multi-configuration Dirac-Fock method (MCDF), including QED corrections. These calculated values are compared to recent experimental data obtained in the Livermore SuperEBIT electron beam ion trap facility [1].

Santos, J. P., A. M. Costa, M. C. Martins, P. Indelicato, and F. Parente. "K X-Ray Energies and Transition Probabilities for He-, Li- and Be-like Praseodymium ions." Journal of Physics: Conference Series 388 (2012): 152018. AbstractWebsite

Theoretical transition energies and probabilities for He-, Li and Be-like Praseodymium ions are calcu- lated in the framework of the multi-configuration Dirac-Fock method (MCDF), including QED corrections. These calculated values are compared to recent experimental data obtained in the Livermore SuperEBIT electron beam ion trap facility [1].

Santos, J. P., M. Guerra, and F. Parente. "New expression for the K-shell ionization." J. Phys.: Conf. Ser. 388 (2012): 042047. AbstractWebsite

A new expression for the total K-shell ionization cross section by electron impact based on the rela- tivistic extension of the binary encounter Bethe (RBEB) model, valid from ionization threshold up to relativistic energies, is proposed. The new MRBEB expression is used to calculate the K-shell ionization cross sections by electron impact for the selenium atom. Comparison with all, to our knowledge, available experimental data shows good agreement.

Santos, J. P., M. Guerra, and F. Parente. "New expression for the K-shell ionization." Journal of Physics: Conference Series 388 (2012): 042047. AbstractWebsite

A new expression for the total K-shell ionization cross section by electron impact based on the rela- tivistic extension of the binary encounter Bethe (RBEB) model, valid from ionization threshold up to relativistic energies, is proposed. The new MRBEB expression is used to calculate the K-shell ionization cross sections by electron impact for the selenium atom. Comparison with all, to our knowledge, available experimental data shows good agreement.

Marques, J., F. Parente, A. Costa, M. Martins, P. Indelicato, and J. P. Santos. "Decay of the 1s^{2}2s3p ^{3}P_{0} level in Be-like ions." Phys. Rev. A 86 (2012): 052521. AbstractWebsite

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Safari, L., P. Amaro, S. Fritzsche, J. P. Santos, and F. Fratini. "Relativistic total cross section and angular distribution for Rayleigh scattering by atomic hydrogen." Phys. Rev. A 85 (2012): 043406. AbstractWebsite

We study the total cross section and angular distribution in Rayleigh scattering by hydrogen atom in the ground state, within the framework of Dirac relativistic equation and second-order perturbation theory. The relativistic states used for the calculations are obtained by making use of the finite basis-set method and expressed in terms of B splines and B polynomials. We pay particular attention to the effects that arise from higher (nondipole) terms in the expansion of the electron-photon interaction. It is shown that the angular distribution of scattered photons, while symmetric with respect to the scattering angle θ=90∘ within the electric dipole approximation, becomes asymmetric when higher multipoles are taken into account. The analytical expression of the angular distribution is parametrized in terms of Legendre polynomials. Detailed calculations are performed for photons in the energy range 0.5 to 10 keV. When possible, results are compared with previous calculations.

Guerra, M., F. Parente, P. Indelicato, and J. P. Santos. "Modified binary encounter Bethe model for electron-impact ionization." International Journal of Mass Spectrometry 313 (2012): 1. AbstractWebsite

Theoretical expressions for ionization cross sections by electron impact based on the binary encounter Bethe (BEB) model, valid from ionization threshold up to relativistic energies, are proposed.The new modified BEB (MBEB) and its relativistic counterpart (MRBEB) expressions are simpler than the BEB (nonrelativistic and relativistic) expressions because they require only one atomic parameter, namely the binding energy of the electrons to be ionized, and use only one scaling term for the ionization of all sub-shells.The new models are used to calculate the K-, L- and M-shell ionization cross sections by electron impact for several atoms with Z from 6 to 83. Comparisons with all, to the best of our knowledge, available experimental data show that this model is as good or better than other models, with less complexity.

Amaro, Pedro, Sophie Schlesser, Mauro Guerra, Eric-Olivier Le Bigot, Jean-Michel Isac, Pascal Travers, Jose Paulo Santos, Csilla Szabo, Alexandre Gumberidze, and Paul Indelicato. "Absolute Measurement of the Relativistic Magnetic Dipole Transition Energy in Heliumlike Argon." Phys. Rev. Lett. 109 (2012): 043005. AbstractWebsite

The 1s2s 3S1 ! 1s2 1S0 relativistic magnetic dipole transition in heliumlike argon, emitted by the plasma of an electron-cyclotron resonance ion source, has been measured using a double-flat crystal x-ray spectrometer. Such a spectrometer, used for the first time on a highly charged ion transition, provides absolute (reference-free) measurements in the x-ray domain. We find a transition energy of 3104.1605(77) eV (2.5 ppm accuracy). This value is the most accurate, reference-free measurement done for such a transition and is in good agreement with recent QED predictions.

Amaro, Pedro, Sophie Schlesser, Mauro Guerra, Eric-Olivier Le Bigot, Jean-Michel Isac, Pascal Travers, Jose Paulo Santos, Csilla Szabo, Alexandre Gumberidze, and Paul Indelicato. "Absolute Measurement of the Relativistic Magnetic Dipole Transition Energy in Heliumlike Argon." Physical Review Letters 109 (2012): 043005. AbstractWebsite

The 1s2s 3S1 - 1s2 1S0 relativistic magnetic dipole transition in heliumlike argon, emitted by the plasma of an electron-cyclotron resonance ion source, has been measured using a double-flat crystal x-ray spectrometer. Such a spectrometer, used for the first time on a highly charged ion transition, provides absolute (reference-free) measurements in the x-ray domain. We find a transition energy of 3104.1605(77) eV (2.5 ppm accuracy). This value is the most accurate, reference-free measurement done for such a transition and is in good agreement with recent QED predictions.

Santos, J. P., A. M. Costa, M. C. Martins, F. Parente, and P. Indelicato. "Modeling praseodymium K X-ray lines in an electron beam ion trap." Eur. Phys. J. D 66 (2012): 202. AbstractWebsite

We study the most important processes for the creation of excited states in He-like through C- like praseodymium ions from the ions ground configurations, leading to the emission of K X-ray lines. Theoretical values for inner-shell excitation and ionization cross sections, transition probabilities and energies for the deexcitation processes, are calculated in the framework of the multi-configuration Dirac- Fock method, including QED corrections. Using these calculated values, a theoretical Kα X-ray spectrum is obtained, which is compared to recent experimental data obtained in the Livermore Super-EBIT electron beam ion trap facility.

Santos, J. P., A. M. Costa, M. C. Martins, F. Parente, and P. Indelicato. "Modeling praseodymium K X-ray lines in an electron beam ion trap." The European Physical Journal D 66 (2012): 202. AbstractWebsite

We study the most important processes for the creation of excited states in He-like through C- like praseodymium ions from the ions ground configurations, leading to the emission of K X-ray lines. Theoretical values for inner-shell excitation and ionization cross sections, transition probabilities and energies for the deexcitation processes, are calculated in the framework of the multi-configuration Dirac- Fock method, including QED corrections. Using these calculated values, a theoretical Kα X-ray spectrum is obtained, which is compared to recent experimental data obtained in the Livermore Super-EBIT electron beam ion trap facility.

Guerra, M., F. Parente, P. Indelicato, and J. P. Santos. "Modified binary encounter Bethe model for electron-impact ionization." Int. J. Mass Spectrom. 313 (2012): 1. AbstractWebsite

Theoretical expressions for ionization cross sections by electron impact based on the binary encounter Bethe (BEB) model, valid from ionization threshold up to relativistic energies, are proposed.
The new modified BEB (MBEB) and its relativistic counterpart (MRBEB) expressions are simpler than the BEB (nonrelativistic and relativistic) expressions because they require only one atomic parameter, namely the binding energy of the electrons to be ionized, and use only one scaling term for the ionization of all sub-shells.
The new models are used to calculate the K-, L- and M-shell ionization cross sections by electron impact for several atoms with Z from 6 to 83. Comparisons with all, to the best of our knowledge, available experimental data show that this model is as good or better than other models, with less complexity.

Safari, L., P. Amaro, S. Fritzsche, J. P. Santos, and F. Fratini. "Relativistic total cross section and angular distribution for Rayleigh scattering by atomic hydrogen." Physical Review A 85 (2012): 043406. AbstractWebsite

We study the total cross section and angular distribution in Rayleigh scattering by hydrogen atom in the ground state, within the framework of Dirac relativistic equation and second-order perturbation theory. The relativistic states used for the calculations are obtained by making use of the finite basis-set method and expressed in terms of B splines and B polynomials. We pay particular attention to the effects that arise from higher (nondipole) terms in the expansion of the electron-photon interaction. It is shown that the angular distribution of scattered photons, while symmetric with respect to the scattering angle θ=90∘ within the electric dipole approximation, becomes asymmetric when higher multipoles are taken into account. The analytical expression of the angular distribution is parametrized in terms of Legendre polynomials. Detailed calculations are performed for photons in the energy range 0.5 to 10 keV. When possible, results are compared with previous calculations.

Guimarães, D., M. L. Carvalho, M. Becker, A. von Bohlen, V. Geraldes, I. Rocha, and J. P. Santos. "Lead concentration in feces and urine of exposed rats by x-ray fluorescence and electrothermal atomic absorption spectrometry." X-Ray Spectrom. 41 (2012): 80. Abstract

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Palma, M. L., and J. P. Santos. "Nuclear spin–spin constants, rotational g factor and susceptibility of sulphur hexafluoride." Mol. Phys. 110 (2012): 2163. AbstractWebsite

Following our previous study on spin–rotation and shielding constants of the SF6 molecule, the rotational g factor and the magnetic susceptibility are calculated here, using ab initio methods to evaluate the electronic contribution to the nuclear hyperfine constants, and compared with experimental results. It is shown, for the first time, that the electronic component of the rotational g factor is proportional to a constant, which is given by a sum over electronic states. We also evaluate for the SF6 molecule the indirect, or electron-coupled spin–spin interaction, theoretically described by Ramsey, and show that it gives non-negligible corrections to direct coupling constants d1 and d2. The contributions of the terms included in this interaction (DSO, PSO, SD and FC) are also analysed.

Guimarães, D., M. L. Carvalho, V. Geraldes, I. Rocha, and J. P. Santos. "Study of lead accumulation in bones of Wistar rats by X-ray fluorescence analysis: aging effect." Metallomics 4 (2012): 66. AbstractWebsite

The accumulation of lead in several bones of Wistar rats with time was determined and compared Q3 for the different types of bones. Two groups were studied: a control group (n = 20), not exposed to lead and a contaminated group (n = 30), exposed to lead from birth, first indirectly through
mother’s milk, and then directly through a diet containing lead acetate in drinking water (0.2%). Rats age ranged from 1 to 11 months, with approximately 1 month intervals and each of the collections had 3 contaminated rats and 2 control rats. Iliac, femur, tibia–fibula and skull have been analysed by energy dispersive X-ray fluorescence technique (EDXRF). Samples of formaldehyde used to preserve the bone tissues were also analysed by Electrothermal Atomic Absorption (ETAAS), showing that there was no significant loss of lead from the tissue to the preservative. The bones mean lead concentration of exposed rats range from 100 to 300 mg g 1 while control rats never exceeded 10 mg g 1. Mean bone lead concentrations were compared and
the concentrations were higher in iliac, femur and tibia–fibula and after that skull. However, of all the concentrations in the different collections, only those in the skull were statistically Q4 significantly different (p o 0.05) from the other types of bones. Analysis of a radar chart also allowed us to say that these differences tend to diminish with age. The Spearman correlation test applied to mean lead concentrations showed strong and very strong positive correlations between
all different types of bones. This test also showed that mean lead concentrations in bones are negatively correlated with the age of the animals. This correlation is strong in iliac and femur and very strong in tibia–fibula and skull. It was also shown that the decrease of lead accumulation with age is made by three plateaus of accumulation,

Pinto, R. M., A. A. Dias, M. Coreano, M. de Simone, B. M. Giuliano, J. P. Santos, and M. L. Costa. "Tautomerism in 5-aminotetrazole investigated by core-level photoelectron spectroscopy and ΔSCF calculations." J. Electron. Spectrosc. Related Phenomena 185 (2012): 13-17. AbstractWebsite

The C 1s and N 1s photoelectron spectra of gas-phase 5-aminotetrazole (5ATZ) were recorded using synchrotron radiation, with the aim of evaluating 1H/2H tautomer population ratios. The core-electron binding energies (CEBEs) were estimated from computational results, using the delta self-consistent-field (ΔSCF) approach. Simulated spectra were generated using these CEBEs and the results from Gaussian-n (Gn, n=1, 2 and 3) and Complete Basis Set (CBS-4M and CBS-Q) methods. Results reveal the almost exclusive predominance of the 2H-tautomer, with a 1H/2H ratio of ca. 0.12/0.88, taken from a gross analysis of the XPS C 1s spectrum, recorded at 365 K.

Guimarães, D., M. L. Carvalho, M. Becker, A. von Bohlen, V. Geraldes, I. Rocha, and J. P. Santos. "Lead concentration in feces and urine of exposed rats by x-ray fluorescence and electrothermal atomic absorption spectrometry." X-Ray Spectrometry 41 (2012): 80. AbstractWebsite

Measurements made in feces and urine of Wistar rats exposed to lead acetate (n = 20) in drinking water since the fetal period were compared with those obtained from a control group (n = 20) in order to assess the age influence on Pb excretion. The measurements were made in different collections of rats aging between 1 and 11 months. To determine the Pb content of the samples, total reflection X-ray fluorescence (TXRF) and electrothermal atomic absorption spectrometry (ETAAS) were used for the urine samples and energy dispersive X-ray fluorescence (EDXRF) was used for the feces.The results show high concentrations of Pb being eliminated from the organism by urine and feces in contaminated rats. Values vary from (600`140)mgl1 to (5 460`115)mgl1 in urine and from (4 500`300)mgg1 to (11 400`3 300)mgg1 in dry feces. The control rats show, in general, low lead concentrations or below detection limits. The fecal/urinary ratio was studied. It was shown to be about three to four orders of magnitude and positively correlated with time. It was verified in feces and urine that excretion decreases with the animal age and that this decrease is made by different levels of excretion. The excretions of Pb in urine and in feces are positively correlated.A good agreement was found between the results obtained with TXRF and ETAAS for urine samples. This work also stresses the suitability of these techniques in the study of Pb intoxication.

Palma, M. L., and J. P. Santos. "Nuclear spin–spin constants, rotational g factor and susceptibility of sulphur hexafluoride." Molecular Physics 110 (2012): 2163. AbstractWebsite

Following our previous study on spin–rotation and shielding constants of the SF6 molecule, the rotational g factor and the magnetic susceptibility are calculated here, using ab initio methods to evaluate the electronic contribution to the nuclear hyperfine constants, and compared with experimental results. It is shown, for the first time, that the electronic component of the rotational g factor is proportional to a constant, which is given by a sum over electronic states. We also evaluate for the SF6 molecule the indirect, or electron-coupled spin–spin interaction, theoretically described by Ramsey, and show that it gives non-negligible corrections to direct coupling constants d1 and d2. The contributions of the terms included in this interaction (DSO, PSO, SD and FC) are also analysed.

Guimarães, D., M. L. Carvalho, V. Geraldes, I. Rocha, and J. P. Santos. "Study of lead accumulation in bones of Wistar rats by X-ray fluorescence analysis: aging effect." Metallomics 4 (2012): 66. AbstractWebsite

The accumulation of lead in several bones of Wistar rats with time was determined and compared Q3 for the different types of bones. Two groups were studied: a control group (n = 20), not exposed to lead and a contaminated group (n = 30), exposed to lead from birth, first indirectly throughmother’s milk, and then directly through a diet containing lead acetate in drinking water (0.2%). Rats age ranged from 1 to 11 months, with approximately 1 month intervals and each of the collections had 3 contaminated rats and 2 control rats. Iliac, femur, tibia–fibula and skull have been analysed by energy dispersive X-ray fluorescence technique (EDXRF). Samples of formaldehyde used to preserve the bone tissues were also analysed by Electrothermal Atomic Absorption (ETAAS), showing that there was no significant loss of lead from the tissue to the preservative. The bones mean lead concentration of exposed rats range from 100 to 300 mg g 1 while control rats never exceeded 10 mg g 1. Mean bone lead concentrations were compared andthe concentrations were higher in iliac, femur and tibia–fibula and after that skull. However, of all the concentrations in the different collections, only those in the skull were statistically Q4 significantly different (p o 0.05) from the other types of bones. Analysis of a radar chart also allowed us to say that these differences tend to diminish with age. The Spearman correlation test applied to mean lead concentrations showed strong and very strong positive correlations betweenall different types of bones. This test also showed that mean lead concentrations in bones are negatively correlated with the age of the animals. This correlation is strong in iliac and femur and very strong in tibia–fibula and skull. It was also shown that the decrease of lead accumulation with age is made by three plateaus of accumulation,