espanolEn este trabajo estudiamos la influencia del conjunto de bases de orbitales atomicos sobre... more espanolEn este trabajo estudiamos la influencia del conjunto de bases de orbitales atomicos sobre la determinacion de la curva de energia potencial (CEP) correspondiente al estado fundamental (formula) de la molecula diatomica Hidruro de Litio. La energia electronica del LiH es calculada, en los marcos de la aproximacion Born-Oppenheimer, a nivel ICC usando los conjuntos de funciones base cc-pVXZ (X=D, T and Q). A partir de las CEP calculadas, determinamos los niveles de energia vibracional y respectivas constantes espectroscopicas. Los resultados obtenidos son comparados con valores experimentales y teoricos publicados previamente. EnglishIn this work we stufy the influence of atomic orbital bases sets in the determination of ground state (formule) potential energy curve of Lithium Hydride diatomic molecule. The electronic energies of LiH are calculated, within the Born-Oppenheimer approximation, at the full Configuration Interaction level using cc-pVXZ (X=D, T and Q) basis sets. F...
We give a basic explanation for the oscillating properties of some physical quantities of a two-e... more We give a basic explanation for the oscillating properties of some physical quantities of a two-electron quantum dot in the presence of a static magnetic field. This behaviour was discussed in a previous work of ours [AM Maniero, et al. J. Phys. B: At. Mol. Opt. Phys. 53:185001, 2020] and was identified as a manifestation of the de Haas-van Alphen effect, originally observed in the framework of diamagnetism of metals in the 30's. We show that this behaviour is a consequence of different eigenstates of the system assuming, in a certain interval of the magnetic field, the condition of the lowest energy singlet and triplet states.
Journal of Physics B: Atomic, Molecular and Optical Physics
We have developed a computational code based on the Hartree–Fock and full interaction configurati... more We have developed a computational code based on the Hartree–Fock and full interaction configuration approaches which allows the study of N-electron confined quantum systems with different confining potentials and external conditions. The code employs Cartesian anisotropic Gaussian-type orbitals as the atomic basis set, which enables the use of different exponents for each direction space in order to better exploit the characteristics of the confining potential. As an illustration, we have employed it to study a system consisting of two electrons confined by a three-dimensional harmonic potential for different values of confinement strength, leading to different confinement conditions: an isotropic three-dimensional and an anisotropic oblate (or quasi-two dimensional) quantum dot. A central aspect of this study is to propose efficient procedures for choosing the exponents of the atomic basis functions. In particular, we note that the use of more than one function for each atomic orbital can improve the convergence of the electronic energy levels. The present results are compared with other theoretical values published previously.
ABSTRACT We propose a two-step genetic algorithm (GA) to fit potential energy curves to both ab i... more ABSTRACT We propose a two-step genetic algorithm (GA) to fit potential energy curves to both ab initio and spectroscopic data. In the first step, the GA is applied to fit only the ab initio points; the parameters of the potential so obtained are then used in the second-step GA optimization, where both ab initio and spectroscopic data are included in the fitting procedure. We have tested this methodology for the extended-Rydberg function, but it can be applied to other functions providing they are sufficiently flexible to fit the data. The results for NaLi and Ar2 diatomic molecules show that the present method provides an efficient way to obtain diatomic potentials with spectroscopic accuracy.
A new potential energy surface is proposed for the ground electronic state of LiH2 and the quantu... more A new potential energy surface is proposed for the ground electronic state of LiH2 and the quantum wave packet calculation for LiH+H reaction is performed. The full configuration interaction method and an aug-cc-pVQZ basis set are employed to calculate the potential energy for a set of criteriously selected geometries. The many-body expansion procedure is used to describe the analytical PES
Journal of Physics B: Atomic, Molecular and Optical Physics, 2001
A procedure to use a configuration-interaction (CI) wavefunction of the target to determine the p... more A procedure to use a configuration-interaction (CI) wavefunction of the target to determine the potential interaction in the electron-molecule collision theory is proposed. Static, exchange and polarization contributions are obtained explicitly. As a first application the method is used to study elastic scattering by two molecules with different symmetries, H2 and CH4. Differential cross sections (DCS) using Hartree-Fock (HF) and
A procedure to use configuration-interaction (CI) target wave-functions in the electron–molecule ... more A procedure to use configuration-interaction (CI) target wave-functions in the electron–molecule collision theory is applied to study the elastic e−–N2 scattering in the (5–20) eV incident energy range. Correlated static and exchange contributions to the interaction potential are presented. Two different atomic basis sets are used. Differential cross sections (DCS) obtained by using Hartree–Fock or CI wave-functions are presented and compared. In the CI case, single and double, and single, double and triple excitations are considered. The effect of electron correlation is analyzed in all the cases. The continuum wave-functions were obtained via the Schwinger variational iterative method. The influence on the DCS of both the size of the atomic basis set and the inclusion of higher-order excitations in the CI calculation is discussed.
A procedure to use configuration-interaction (CI) target wave-functions in the electron–molecule ... more A procedure to use configuration-interaction (CI) target wave-functions in the electron–molecule collision theory is applied to study the elastic e−–N2 scattering in the (5–20) eV incident energy range. Correlated static and exchange contributions to the interaction potential are presented. Two different atomic basis sets are used. Differential cross sections (DCS) obtained by using Hartree–Fock or CI wave-functions are presented and compared. In the CI case, single and double, and single, double and triple excitations are considered. The effect of electron correlation is analyzed in all the cases. The continuum wave-functions were obtained via the Schwinger variational iterative method. The influence on the DCS of both the size of the atomic basis set and the inclusion of higher-order excitations in the CI calculation is discussed.
Photoionization and photofragmentation studies of formic acid (HCOOH) are performed for the valen... more Photoionization and photofragmentation studies of formic acid (HCOOH) are performed for the valence shell electron ionization process. The total and partial ion yield of gaseous HCOOH were collected as a function of photon energy in the ultraviolet region, between 11.12 and 19.57 eV. Measurements of the total and partial ion yield of gaseous formic acid molecule are performed with a time-of-flight mass spectrometer at the Synchrotron Light Brazilian Laboratory. Density functional theory and time dependent density functional theory are employed to calculate the ground and excited electronic state energies of neutral and ionic formic acid as well as their fragments and normal vibration modes. The ionization potential energies, the stability of electronic excited states of HCOOH(+), and the energies of opening fragmentation channels are estimated from theoretical-experimental analysis. Additionally, the main formic acid photofragmentation pathways by exposition of photons within that energy range are determined experimentally. These produced ions primarily have the following mass/charge ratios: 46 (HCOOH(+)), 45 (COOH(+)), 29 (HCO(+)), and 18 (H(2)O(+)).
espanolEn este trabajo estudiamos la influencia del conjunto de bases de orbitales atomicos sobre... more espanolEn este trabajo estudiamos la influencia del conjunto de bases de orbitales atomicos sobre la determinacion de la curva de energia potencial (CEP) correspondiente al estado fundamental (formula) de la molecula diatomica Hidruro de Litio. La energia electronica del LiH es calculada, en los marcos de la aproximacion Born-Oppenheimer, a nivel ICC usando los conjuntos de funciones base cc-pVXZ (X=D, T and Q). A partir de las CEP calculadas, determinamos los niveles de energia vibracional y respectivas constantes espectroscopicas. Los resultados obtenidos son comparados con valores experimentales y teoricos publicados previamente. EnglishIn this work we stufy the influence of atomic orbital bases sets in the determination of ground state (formule) potential energy curve of Lithium Hydride diatomic molecule. The electronic energies of LiH are calculated, within the Born-Oppenheimer approximation, at the full Configuration Interaction level using cc-pVXZ (X=D, T and Q) basis sets. F...
We give a basic explanation for the oscillating properties of some physical quantities of a two-e... more We give a basic explanation for the oscillating properties of some physical quantities of a two-electron quantum dot in the presence of a static magnetic field. This behaviour was discussed in a previous work of ours [AM Maniero, et al. J. Phys. B: At. Mol. Opt. Phys. 53:185001, 2020] and was identified as a manifestation of the de Haas-van Alphen effect, originally observed in the framework of diamagnetism of metals in the 30's. We show that this behaviour is a consequence of different eigenstates of the system assuming, in a certain interval of the magnetic field, the condition of the lowest energy singlet and triplet states.
Journal of Physics B: Atomic, Molecular and Optical Physics
We have developed a computational code based on the Hartree–Fock and full interaction configurati... more We have developed a computational code based on the Hartree–Fock and full interaction configuration approaches which allows the study of N-electron confined quantum systems with different confining potentials and external conditions. The code employs Cartesian anisotropic Gaussian-type orbitals as the atomic basis set, which enables the use of different exponents for each direction space in order to better exploit the characteristics of the confining potential. As an illustration, we have employed it to study a system consisting of two electrons confined by a three-dimensional harmonic potential for different values of confinement strength, leading to different confinement conditions: an isotropic three-dimensional and an anisotropic oblate (or quasi-two dimensional) quantum dot. A central aspect of this study is to propose efficient procedures for choosing the exponents of the atomic basis functions. In particular, we note that the use of more than one function for each atomic orbital can improve the convergence of the electronic energy levels. The present results are compared with other theoretical values published previously.
ABSTRACT We propose a two-step genetic algorithm (GA) to fit potential energy curves to both ab i... more ABSTRACT We propose a two-step genetic algorithm (GA) to fit potential energy curves to both ab initio and spectroscopic data. In the first step, the GA is applied to fit only the ab initio points; the parameters of the potential so obtained are then used in the second-step GA optimization, where both ab initio and spectroscopic data are included in the fitting procedure. We have tested this methodology for the extended-Rydberg function, but it can be applied to other functions providing they are sufficiently flexible to fit the data. The results for NaLi and Ar2 diatomic molecules show that the present method provides an efficient way to obtain diatomic potentials with spectroscopic accuracy.
A new potential energy surface is proposed for the ground electronic state of LiH2 and the quantu... more A new potential energy surface is proposed for the ground electronic state of LiH2 and the quantum wave packet calculation for LiH+H reaction is performed. The full configuration interaction method and an aug-cc-pVQZ basis set are employed to calculate the potential energy for a set of criteriously selected geometries. The many-body expansion procedure is used to describe the analytical PES
Journal of Physics B: Atomic, Molecular and Optical Physics, 2001
A procedure to use a configuration-interaction (CI) wavefunction of the target to determine the p... more A procedure to use a configuration-interaction (CI) wavefunction of the target to determine the potential interaction in the electron-molecule collision theory is proposed. Static, exchange and polarization contributions are obtained explicitly. As a first application the method is used to study elastic scattering by two molecules with different symmetries, H2 and CH4. Differential cross sections (DCS) using Hartree-Fock (HF) and
A procedure to use configuration-interaction (CI) target wave-functions in the electron–molecule ... more A procedure to use configuration-interaction (CI) target wave-functions in the electron–molecule collision theory is applied to study the elastic e−–N2 scattering in the (5–20) eV incident energy range. Correlated static and exchange contributions to the interaction potential are presented. Two different atomic basis sets are used. Differential cross sections (DCS) obtained by using Hartree–Fock or CI wave-functions are presented and compared. In the CI case, single and double, and single, double and triple excitations are considered. The effect of electron correlation is analyzed in all the cases. The continuum wave-functions were obtained via the Schwinger variational iterative method. The influence on the DCS of both the size of the atomic basis set and the inclusion of higher-order excitations in the CI calculation is discussed.
A procedure to use configuration-interaction (CI) target wave-functions in the electron–molecule ... more A procedure to use configuration-interaction (CI) target wave-functions in the electron–molecule collision theory is applied to study the elastic e−–N2 scattering in the (5–20) eV incident energy range. Correlated static and exchange contributions to the interaction potential are presented. Two different atomic basis sets are used. Differential cross sections (DCS) obtained by using Hartree–Fock or CI wave-functions are presented and compared. In the CI case, single and double, and single, double and triple excitations are considered. The effect of electron correlation is analyzed in all the cases. The continuum wave-functions were obtained via the Schwinger variational iterative method. The influence on the DCS of both the size of the atomic basis set and the inclusion of higher-order excitations in the CI calculation is discussed.
Photoionization and photofragmentation studies of formic acid (HCOOH) are performed for the valen... more Photoionization and photofragmentation studies of formic acid (HCOOH) are performed for the valence shell electron ionization process. The total and partial ion yield of gaseous HCOOH were collected as a function of photon energy in the ultraviolet region, between 11.12 and 19.57 eV. Measurements of the total and partial ion yield of gaseous formic acid molecule are performed with a time-of-flight mass spectrometer at the Synchrotron Light Brazilian Laboratory. Density functional theory and time dependent density functional theory are employed to calculate the ground and excited electronic state energies of neutral and ionic formic acid as well as their fragments and normal vibration modes. The ionization potential energies, the stability of electronic excited states of HCOOH(+), and the energies of opening fragmentation channels are estimated from theoretical-experimental analysis. Additionally, the main formic acid photofragmentation pathways by exposition of photons within that energy range are determined experimentally. These produced ions primarily have the following mass/charge ratios: 46 (HCOOH(+)), 45 (COOH(+)), 29 (HCO(+)), and 18 (H(2)O(+)).
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Papers by Angelo M Maniero