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Pessanha, S., C. Fonseca, J. P. Santos, M. L. Carvalho, and A. A. Dias. "Comparison of standard-based and standardless methods of quantification used in X-ray fluorescence analysis: Application to the exoskeleton of clams." X-Ray Spectrom. 47 (2018): 108-115. Abstract

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Pessanha, Sofia, Ana Samouco, Ricardo Adão, Maria Luisa Carvalho, Jose Paulo Santos, and Pedro Amaro. "Detection limits evaluation of a portable energy dispersive X-ray fluorescence setup using different filter combinations." X-Ray Spectrometry 46 (2017): 102-106. AbstractWebsite

In this paper, we study the performance of a portable energy dispersive X‐ray fluorescence spectrometer by making use of different filter configurations at the X‐ray tube output. To fulfill this purpose,...

Pinto, R. M., A. A. Dias, M. Coreno, M. de Simone, B. M. Giuliano, J. P. Santos, and M. L. Costa. "Tautomerism in 5-methyltetrazole investigated by core-level photoelectron spectroscopy and ΔSCF calculations." Chemical Physics Letters 516 (2011): 149-153. AbstractWebsite

The relative populations of the 1H- and 2H-tautomer of gas-phase 5-methyltetrazole (5MTZ) have been assessed through core-level photoelectron spectroscopy, and compared with the results obtained from Gaussian-n (Gn, n = 1, 2 and 3) and Complete Basis Set methods (CBS-4M and CBS-Q). The C 1s and N 1s core‚Äìelectron binding energies (CEBEs) for each ionization site of both tautomers have been computed using the Œîself-consistent-field (ŒîSCF) approach. The C 1s and N 1s XPS spectra, obtained at 313 K, yield a 1H/2H tautomer ratio of ca. 0.16/0.84 and 0.21/0.79, respectively.

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.

Pinto, R. M., A. A. Dias, M. Coreno, 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." Journal of Electron Spectroscopy and 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.

Pinto, R. M., A. A. Dias, M. L. Costa, and J. P. Santos. "Computational study on the ionization energies of benzyl azide and its methyl derivatives." Journal of Molecular Structure: THEOCHEM 948 (2010): 15-20. AbstractWebsite
Ionization energies of benzyl azide (BA), C6H5CH2N3, its methyl derivatives, 2-, 3- and 4-methyl benzyl azide and (1-azidoethyl)benzene (2-, 3- and 4-MBA and 1-AEB), (CH3)C6H4CH2 N3, have been calculated with several basis sets, with M¯ller-Plesset and Hartree-Fock methods. The data are compared to the ionizations energies obtained from HeI photoelectron spectroscopy (UVPES) experiments, in order to support the correct assignment of the bands. The nature and character of the molecular orbitals are also discussed.
Pinto, R. M., A. A. Dias, M. Coreno, M. de Simone, B. M. Giuliano, J. P. Santos, and M. L. Costa. "Tautomerism in 5-methyltetrazole investigated by core-level photoelectron spectroscopy and ΔSCF calculations." Chemical Physics Letters 516 (2011): 149-153. AbstractWebsite

Chemical Physics Letters, 516 (2011) 149-153. doi:10.1016/j.cplett.2011.10.001

Pinto, R. M., A. A. Dias, M. Coreno, M. de Simone, B. M. Giuliano, J. P. Santos, and M. L. Costa. "Tautomerism in 5-methyltetrazole investigated by core-level photoelectron spectroscopy and ΔSCF calculations." Chemical Physics Letters 516 (2011): 149-153. AbstractWebsite

The relative populations of the 1H- and 2H-tautomer of gas-phase 5-methyltetrazole (5MTZ) have been assessed through core-level photoelectron spectroscopy, and compared with the results obtained from Gaussian-n (Gn, n = 1, 2 and 3) and Complete Basis Set methods (CBS-4M and CBS-Q). The C 1s and N 1s core‚Äìelectron binding energies (CEBEs) for each ionization site of both tautomers have been computed using the Œîself-consistent-field (ŒîSCF) approach. The C 1s and N 1s XPS spectra, obtained at 313 K, yield a 1H/2H tautomer ratio of ca. 0.16/0.84 and 0.21/0.79, respectively.

Pinto, R. M., A. A. Dias, and M. L. Costa. "Theoretical study of the molecular properties of methyl 2-azidopropionate and methyl 3-azidopropionate." Journal of Molecular Structure: THEOCHEM 894 (2009): 80-87. AbstractWebsite

An extensive conformational analysis was carried at ab initio and DFT levels of theory on two molecules - methyl 2-azidopropionate (N3CH3CHCOOCH3) and methyl 3-azidopropionate (N3CH2CH2COOCH3). In each case, the lowest energy conformers were characterized and the energy barriers between them were estimated. Ionization energies and vibrational frequencies were also computed, in order to support future spectroscopic studies with ultraviolet photoelectron spectroscopy (UVPES) and matrix isolation infrared spectroscopy (Matrix Isolation FTIR).

Pinto, R. M., R. I. Olariu, J. Lameiras, F. T. Martins, A. A. Dias, G. J. Langley, P. Rodrigues, C. D. Maycock, J. P. Santos, M. F. Duarte, M. T. Fernandez, and M. L. Costa. "Study of selected benzyl azides by UV photoelectron spectroscopy and mass spectrometry." Journal of Molecular Structure 980 (2010): 163-171. AbstractWebsite

Benzyl azide and the three methylbenzyl azides were synthesized and characterized by mass spectrometry (MS) and ultraviolet photoelectron spectroscopy (UVPES). The electron ionization fragmentation mechanisms for benzyl azide and their methyl derivatives were studied by accurate mass measurements and linked scans at constant B/E. For benzyl azide, in order to clarify the fragmentation mechanism, labelling experiments were performed. From the mass analysis of methylbenzyl azides isomers it was possible to differentiate the isomers ortho, meta and para. The abundance and nature of the ions resulting from the molecular ion fragmentation, for the three distinct isomers of substituted benzyl azides, were rationalized in terms of the electronic properties of the substituent. Concerning the para-isomer, IRC calculations were performed at UHF/6-31G(d) level. The photoionization study of benzyl azide, with He(I) radiation, revealed five bands in the 8-21 eV ionization energies region. From every photoelectron spectrum of methylbenzyl azides isomers it has been identified seven bands, on the same range as the benzyl azide. Interpretation of the photoelectron spectra was accomplished applying Koopmans' theorem to the SCF orbital energies obtained at HF/6-311++G(d, p) level.

Pinto, R. M., R. I. Olariu, J. Lameiras, F. T. Martins, A. A. Dias, G. J. Langley, P. Rodrigues, C. D. Maycock, J. P. Santos, M. F. Duarte, M. T. Fernandez, and M. L. Costa. "Study of selected benzyl azides by UV photoelectron spectroscopy and mass spectrometry." Journal of Molecular Structure 980 (2010): 163-171. AbstractWebsite
Benzyl azide and the three methylbenzyl azides were synthesized and characterized by mass spectrometry (MS) and ultraviolet photoelectron spectroscopy (UVPES). The electron ionization fragmentation mechanisms for benzyl azide and their methyl derivatives were studied by accurate mass measurements and linked scans at constant B/E. For benzyl azide, in order to clarify the fragmentation mechanism, labelling experiments were performed. From the mass analysis of methylbenzyl azides isomers it was possible to differentiate the isomers ortho, meta and para. The abundance and nature of the ions resulting from the molecular ion fragmentation, for the three distinct isomers of substituted benzyl azides, were rationalized in terms of the electronic properties of the substituent. Concerning the para-isomer, IRC calculations were performed at UHF/6-31G(d) level. The photoionization study of benzyl azide, with He(I) radiation, revealed five bands in the 8-21 eV ionization energies region. From every photoelectron spectrum of methylbenzyl azides isomers it has been identified seven bands, on the same range as the benzyl azide. Interpretation of the photoelectron spectra was accomplished applying Koopmans' theorem to the SCF orbital energies obtained at HF/6-311++G(d, p) level.
Pinto, R. M., A. A. Dias, M. L. Costa, and J. P. Santos. "Computational study on the ionization energies of benzyl azide and its methyl derivatives." Journal of Molecular Structure: THEOCHEM 948 (2010): 15-20. AbstractWebsite

Ionization energies of benzyl azide (BA), C6H5CH2N3, its methyl derivatives, 2-, 3- and 4-methyl benzyl azide and (1-azidoethyl)benzene (2-, 3- and 4-MBA and 1-AEB), (CH3)C6H4CH2 N3, have been calculated with several basis sets, with M¯ller-Plesset and Hartree-Fock methods. The data are compared to the ionizations energies obtained from HeI photoelectron spectroscopy (UVPES) experiments, in order to support the correct assignment of the bands. The nature and character of the molecular orbitals are also discussed.

Pohl, Randolf, François Nez, Luis M. P. Fernandes, Marwan Abdou Ahmed, Fernando D. Amaro, Pedro Amaro, François Biraben, João M. R. Cardoso, Daniel S. Covita, Andreas Dax, Satish Dhawan, Marc Diepold, Beatrice Franke, Sandrine Galtier, Adolf Giesen, Andrea L. Gouvea, Johannes Götzfried, Thomas Graf, Theodor W. Hänsch, Malte Hildebrandt, Paul Indelicato, Lucile Julien, Klaus Kirch, Andreas Knecht, Paul Knowles, Franz Kottmann, Julian J. Krauth, Eric-Olivier Le Bigot, Yi-Wei Liu, José A. M. Lopes, Livia Ludhova, Jorge Machado, Cristina M. B. Monteiro, Françoise Mulhauser, Tobias Nebel, Paul Rabinowitz, Joaquim M. F. dos Santos, Jose Paulo Santos, Lukas A. Schaller, Karsten Schuhmann, Catherine Schwob, Csilla I. Szabo, David Taqqu, João F. C. A. Veloso, Andreas Voss, Birgit Weichelt, and Aldo Antognini. "Laser Spectroscopy of Muonic Atoms and Ions." In Proceedings of the 12th International Conference on Low Energy Antiproton Physics (LEAP2016), 1-12. Journal of the Physical Society of Japan, 2017. Abstract
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Pohl, R., and CREMA Collaboration. "Laser Spectroscopy of Muonic Atoms and Ions." JPS Conf. Proc. (2016): 1-12. AbstractWebsite
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Rahangdale, H. V., D. Mitra, P. K. Das, S. De, M. Guerra, J. P. Santos, and S. Saha. "Spectroscopic investigations of L-shell ionization in heavy elements by electron impact." Journal of Quantitative Spectroscopy and Radiative Transfer 174 (2016): 79-87. AbstractWebsite

Journal of Quantitative Spectroscopy and Radiative Transfer, 174 + (2016) 79-87. doi:10.1016/j.jqsrt.2016.01.026

Rahangdale, H. V., M. Guerra, P. K. Das, S. De, J. P. Santos, D. Mitra, and S. Saha. "Determination of subshell-resolved <span class="aps-inline-formula"><math><mi>L</mi></math></span>-shell-ionization cross sections of gold induced by 15–40-keV electrons." Physical Review A 89 (2014): 052708. AbstractWebsite
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Rahangdale, H. V., D. Mitra, M. Guerra, J. P. Santos, and S. Saha. "Subshell resolved inner shell ionization cross-sections of High Z elements by electron impact." Journal of Physics: Conference Series 635 (2015): 052001-2. AbstractWebsite
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Rahangdale, H. V., M. Guerra, P. K. Das, S. De, J. P. Santos, D. Mitra, and S. Saha. "Determination of subshell-resolved <span class="aps-inline-formula"><math><mi>L</mi></math></span>-shell-ionization cross sections of gold induced by 15–40-keV electrons." Physical Review A 89 (2014): 052708. AbstractWebsite
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Ramos, I., I. M. Pataco, M. P. Mourinho, F. Lidon, F. Reboredo, M. F. Pessoa, M. L. Carvalho, J. P. Santos, and M. Guerra. "Elemental mapping of biofortified wheat grains using micro X-ray fluorescence." Spectrochimica Acta Part B: Atomic Spectroscopy 120 (2016): 30-36. AbstractWebsite

Spectrochimica Acta Part B: Atomic Spectroscopy, 120 (2016) 30-36. doi:10.1016/j.sab.2016.03.014

Reboredo, {Fernando Henrique}, A. Barbosa, {Maria Manuela} Silva, {Maria Luisa} Carvalho, {José Paulo} Santos, {Maria Fernanda} Pessoa, Fernando Lidon, {José C. } Ramalho, and Mauro Guerra. "Mineral Content of Food Supplements of Plant Origin, by Energy Dispersive X-ray Fluorescence: A Risk Assessment." Exposure and Health 12 (2020): 917-927. Abstract

The aim of this study is to evaluate the elemental composition of six food supplements of plant origin, commonly sold in the Portuguese market, by energy dispersive X-ray fluorescence. The presence of arsenic in all the Maca, Ashwagandha, Camu-Camu and Hemp protein samples (except the generic form) is a reason of concern due to the long-term effects of As mainly in its inorganic form. Thus, great caution must be taken on some food supplements, particularly the cases of Moringa from Egypt and Yellow/Xpresso Maca, whose inorganic As concentrations are in line with the upper bound concentration for the 95th dietary exposure according to the European Food Safety Authority which is 0.64 μg/kg bw/day. In what regards Hemp protein, if the supplier’s daily intake recommendation (30 g) is followed, values as high as 1.75 μg/kg bw/day of inorganic As will be consumed, which are dangerously above the upper bound. In this case this specific supplement lot should be removed from the market. Also the consumption of Hemp protein leads to a daily intake of Mn above the Daily Reference Intake (DRI) and Adequate Intakes (AIs) for adults. The contamination of Goji berries by Pb is a reason for concern—organic berries contained 11.3 μg/g while berries derived from conventional agriculture 11.6 μg/g, leading to daily intake doses of 315.3 μg and 324.8 μg, respectively, if the recommended daily intake of 28 g is followed. Our findings point out to an inadequacy of the recommended intakes by the supplier vis a vis the concentrations observed, greatly increasing the risk for public health.

Rodrigues, G. C., P. Indelicato, J. P. Santos, P. Patté, and F. Parente. "Systematic calculation of total atomic energies of ground state configurations." Atomic Data and Nuclear Data Tables 86 (2004): 117-233. AbstractWebsite

We present a systematic study of atomic binding energies, in the Dirac–Fock approximation, for the Lithium (3 electrons) to the Dubnium (105 electrons) isoelectronic series. In each series we have considered all atomic numbers from the one corresponding to the neutral atom up to Z=118. We have obtained the ground state configurations for several heavy ions with charge larger than one.

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Safari, L., P. Amaro, J. P. Santos, and F. Fratini. "Angular and polarization analysis for two-photon decay of <span class="aps-inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mn>2</mn><mi>s</mi></mrow></math>&." Physical Review A 90 (2014): 014502. AbstractWebsite

The amplitude of two-photon transitions between hyperfine states in hydrogenlike ions is derived based on the relativistic Dirac equation and second-order perturbation theory. We study angular and linear polarization properties of the photon pair emitted in the decay of $2s$ states, where spin-flip and non-spin-flip transitions are highlighted. We pay particular attention to hydrogenlike uranium, since it is an ideal candidate for investigating relativistic and high-multipole effects, such as spin-flip transitions. Two types of emission patterns are identified: (i) non-spin-flip transitions are found to be characterized by an angular distribution of the type $W($\theta${})$\sim${}1+{cos}^{2}$\theta${}$ while the polarizations of the emitted photons are parallel; and (ii) spin-flip transitions have somewhat smaller decay rates and are found to be characterized by an angular distribution of the type $W($\theta${})$\sim${}1$-${}1/3{cos}^{2}$\theta${}$ while the polarizations of the emitted photons are orthogonal, where $$\theta${}$ is the angle between photons directions. Deviations due to nondipole and relativistic contributions are evaluated for both types of transitions. This work is the first step toward exploring the effect of the nucleus over the angular and polarization properties of the photon pairs emitted by two-photon transitions.

Safari, L., J. P. Santos, P. Amaro, K. Jankala, and F. Fratini. "Analytical evaluation of atomic form factors: Application to Rayleigh scattering." Journal of Mathematical Physics 56 (2015): 052105-9. AbstractWebsite
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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.