Marisa Faraggi - Academia.edu (original) (raw)

Papers by Marisa Faraggi

Research paper thumbnail of Electron emission from metal surfaces by ultra-short pulses

We study electron emission spectra produced by the grazing incidence of ultra-short laser pulses ... more We study electron emission spectra produced by the grazing incidence of ultra-short laser pulses on metal surfaces. To describe this process we introduce a distorted-wave approach, based on a simple description of the solid, which includes the main features of the process, taking into account the contribution of the induced potential. The method is applied to evaluate photoemission from the valence band of Al(111), considering different frequencies and durations of the pulse. The results so obtained are contrasted with the numerical solution to the time-dependent Schrödinger equation (TDSE), finding a very good agreement through the whole energetic range.

Research paper thumbnail of Role of band structure and local-field effects in the low-energy collective electronic excitation spectra of 2<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>H</mml:mi></mml:math>-NbSe<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:...

Physical Review B, Jul 11, 2012

We present a study of the electron dynamics in the layered compound 2H-NbSe 2. First-principles c... more We present a study of the electron dynamics in the layered compound 2H-NbSe 2. First-principles calculations are used to obtain the band structure employed in the evaluation of the loss function with inclusion of local-field (LF) effects. Two different symmetry directions [(100) and (010)] were explored in the hexagonal basal plane. In both cases, a low-energy charge-carrier plasmon (CCP) at ∼1 eV presenting a negative dispersion over a wide momentum transfer range is found, in agreement with recent experimental results [Wezel et al., Phys. Rev. Lett. 107, 176404 (2011)]. On the contrary, in the (001) perpendicular direction, the CCP has negative dispersion at small momenta only, presenting strong positive dispersion at larger momenta. Our calculations reveal that this behavior can be explained without invoking many-body effects, as long as band structure effects are properly included in the evaluation of the excitation spectra. In addition to this CCP mode, we find another one with an arclike oscillating dispersion along the perpendicular direction, as well as the appearance of a CCP replica at high momenta due to LF effects.

Research paper thumbnail of On the stability of the electronic system in transition metal dichalcogenides

Journal of Physics: Condensed Matter, Apr 8, 2016

Research paper thumbnail of Single-molecule enhanced spin-flip detection

arXiv (Cornell University), Nov 2, 2016

We studied the spin-flip excitations of a doubledecker nickelocene molecule (Nc) adsorbed on Cu(1... more We studied the spin-flip excitations of a doubledecker nickelocene molecule (Nc) adsorbed on Cu(100) by means of inelastic tunneling spectroscopy (IETS), X-ray magnetic circular dichroism (XMCD) and density functional theory calculations (DFT). The results show that the molecule preserves its magnetic moment and magnetic anisotropy not only on Cu(100), but also in different metallic environments including the tip apex. Taking advantage of the efficient spin-flip excitation of this molecule, we show how such a molecular functionalized tip boosts the inelastic signal of a surface supported Nc by almost one order of magnitude thanks to a double spin-excitation process.

Research paper thumbnail of Unveiling nickelocene bonding to a noble metal surface

Physical Review B, 2016

The manipulation of a molecular spin state in low-dimensional materials is central to molecular s... more The manipulation of a molecular spin state in low-dimensional materials is central to molecular spintronics. The designs of hybrid devices incorporating magnetic metallocenes are very promising in this regard, but are hampered by the lack of data regarding their interaction with a metal. Here, we combine low-temperature scanning tunneling microscopy and density functional theory calculations to investigate a magnetic metallocene at the single-molecule level-nickelocene. We demonstrate that the chemical and electronic structures of nickelocene are preserved upon adsorption on a copper surface. Several bonding configurations to the surface are identified, ranging from the isolated molecule to molecular layers governed by van der Waals interactions.

Research paper thumbnail of Characterization of an oxalic acid layer on Cu(111)

Research paper thumbnail of The densest iron coordination network based on carboxylate ligands

Trabajo presentado al "11th International Conference on Atomically Controlled Surfaces, Inte... more Trabajo presentado al "11th International Conference on Atomically Controlled Surfaces, Interfaces and Nanostructures" celebrado en San Petersburgo del 3 al 7 de octubre del 2011.-- et al.

Research paper thumbnail of N ov 2 01 6 Single-molecule enhanced spin-flip detection

We studied the spin-flip excitations of a double-decker nickelocene molecule (Nc) adsorbed on Cu(... more We studied the spin-flip excitations of a double-decker nickelocene molecule (Nc) adsorbed on Cu(100) by means of inelastic tunneling spectroscopy (IETS), X-ray magnetic circular dichroism (XMCD) and density functional theory calculations (DFT). The results show that the molecule preserves its magnetic moment and magnetic anisotropy not only on Cu(100), but also in different metallic environments including the tip apex. Taking advantage of the efficient spin-flip excitation of this molecule, we show how such a molecular functionalized tip boosts the inelastic signal of a surface supported Nc by almost one order of magnitude thanks to a double spin-excitation process.

Research paper thumbnail of On the stability of the electronic system in transition metal dichalcogenides

Journal of Physics: Condensed Matter, 2016

Research paper thumbnail of Modeling Ferro- and Antiferromagnetic Interactions in Metal–Organic Coordination Networks

The Journal of Physical Chemistry C, 2014

Magnetization curves of two rectangular metal-organic coordination networks formed by the organic... more Magnetization curves of two rectangular metal-organic coordination networks formed by the organic ligand TCNQ (7,7,8,8-tetracyanoquinodimethane) and two different (Mn and Ni) 3d transition metal atoms [M(3d)] show marked differences that are explained using first principles density functional theory and model calculations. We find that the existence of a weakly dispersive hybrid band with M(3d) and TCNQ character crossing the Fermi level is determinant for the appearance of ferromagnetic coupling between metal centers, as it is the case of the metallic system Ni-TCNQ but not of the insulating system Mn-TCNQ. The spin magnetic moment localized at the Ni atoms induces a significant spin polarization in the organic molecule; the corresponding spin density being delocalized along the whole system. The exchange interaction between localized spins at Ni centers and the itinerant spin density is ferromagnetic. Based on two different model Hamiltonians, we estimate the strength of exchange couplings between magnetic atoms for both Ni-and Mn-TCNQ networks that results in weak ferromagnetic and very weak antiferromagnetic correlations for Ni-and Mn-TCNQ networks, respectively.

Research paper thumbnail of Influence of the surface band structure on electron emission spectra from metal surfaces

Physical Review B, 2014

Electron distributions produced by grazing impact of fast protons on Mg(0001), Cu(111), Ag(111) a... more Electron distributions produced by grazing impact of fast protons on Mg(0001), Cu(111), Ag(111) and Au(111) surfaces are investigated, focusing on the effects of the electronic band structure. The process is described within the Band-Structure-Based approximation, which is a perturbative method that includes an accurate representation of the electron-surface interaction, incorporating information of the electronic band structure of the solid. For all the studied surfaces, the presence of partially occupied surface electronic states produces noticeable structures in double differentialenergy-and angle-resolved-electron emission probabilities from the valence band. These structures remain visible in electron emission spectra after adding contributions coming from core electrons, which might make it possible their experimental detection.

Research paper thumbnail of Interaction of ultrashort laser pulses with metal surfaces: Impulsive jellium-Volkov approximation versus the solution of the time-dependent Schrödinger equation

Physical Review A, 2007

Electron emission coming from the valence band of metal surfaces due to grazing incidence of high... more Electron emission coming from the valence band of metal surfaces due to grazing incidence of highfrequency ultrashort laser pulses is studied. We introduce a distorted-wave method, named impulsive jellium-Volkov ͑IJV͒ approximation, in which the surface is represented by the jellium model while the interaction with the laser field is described by means of the Volkov phase. With the purpose of examining the proposed approach, we compare IJV results with values derived from the numerical solution of the corresponding time-dependent Schrödinger equation ͑TDSE͒. For Al͑111͒ surfaces, double and single differential probability spectra are calculated considering different durations of the laser pulse. Very good agreement between IJV and TDSE results was found. The total probability dependence on the intensity and carrier-envelope phase of the pulse is also investigated.

Research paper thumbnail of Study of the induced potential produced by ultrashort pulses on metal surfaces

Journal of the Optical Society of America B, 2009

The influence of the induced potential on photoelectron emission from metal surfaces is studied f... more The influence of the induced potential on photoelectron emission from metal surfaces is studied for grazing incidence of ultra short laser pulses. To describe this process we introduce a distorted wave-method, the Surface Jellium-Volkov approach, which includes the perturbation on the emitted electron produced by both the laser and the induced fields. The method is applied to an Al(111) surface contrasting the results with the numerical solution to the time-dependent Schrödinger equation (TDSE). We found that SJV approach reproduces well the main features of emission spectra, accounting properly for effects originated by the induced potential.

Research paper thumbnail of Dimensionality reduction to improve search time and memory footprint in content-retrieval tasks: Application to semiconductor inspection images

Advances in Industrial and Manufacturing Engineering

Research paper thumbnail of Efficient Spin-Flip Excitation of a Nickelocene Molecule

Research paper thumbnail of Band-structure-based collisional model for electronic excitations in ion-surface collisions

Physical Review A, 2005

Energy loss per unit path in grazing collisions with metal surfaces is studied by using the colli... more Energy loss per unit path in grazing collisions with metal surfaces is studied by using the collisional and dielectric formalisms. Within both theories we make use of the band-structure-based ͑BSB͒ model to represent the surface interaction. The BSB approach is based on a model potential and provides a precise description of the one-electron states and the surface-induced potential. The method is applied to evaluate the energy lost by 100 keV protons impinging on aluminum surfaces at glancing angles. We found that when the realistic BSB description of the surface is used, the energy loss obtained from the collisional formalism agrees with the dielectric one, which includes not only binary but also plasmon excitations. The distance-dependent stopping power derived from the BSB model is in good agreement with available experimental data. We have also investigated the influence of the surface band structure in collisions with the Al͑100͒ surface. Surface-state contributions to the energy loss and electron emission probability are analyzed.

Research paper thumbnail of Photoelectron emission from metal surfaces by ultrashort laser pulses

Physical Review A, 2006

Electron emission from metal surfaces produced by short laser pulses is studied within the framew... more Electron emission from metal surfaces produced by short laser pulses is studied within the framework of the distorted-wave formulation. The proposed approach, named surface-Volkov ͑SV͒ approximation, makes use of the band-structure based ͑BSB͒ model and the Volkov phase to describe the interaction of the emitted electron with the surface and the external electric field, respectively. The BSB model provides a realistic representation of the surface, based on a model potential that includes the main features of the surface band structure. The SV method is applied to evaluate the photoelectron emission from the valence band of Al͑111͒. Angular and energy distributions are investigated for different parameters of the laser pulse, keeping in all cases the carrier frequency larger than the plasmon one.

Research paper thumbnail of Quantum-mechanical model for valence-electron emission from metal surfaces

Physical Review A

Electron emission from the conduction band of metal surfaces is studied under grazing scattering ... more Electron emission from the conduction band of metal surfaces is studied under grazing scattering conditions. We investigate this process making use of the quantum-mechanical (QM) model to represent the electronic interactions within the binary collisional formalism. The QM approach is based on the use of the model potential and allows us to describe the main features of the metal surface. It provides a precise description of both one-electron states and surface induced potential. In this work, the approximation is employed to evaluate electron distributions for 100 keV protons impinging grazingly on the Al(111) surface. We have found that the realistic representation of the surface included in the QM model introduces substantial changes in the valence emission at low electron energies and intermediate ejection angles. The influence of the surface wake potential on the valence emission probability is also addressed. In order to compare with experiments, we add the contribution coming...

Research paper thumbnail of Quantum-mechanical model for valence-electron emission from metal surfaces

Electron emission from the conduction band of metal surfaces is studied under grazing scattering ... more Electron emission from the conduction band of metal surfaces is studied under grazing scattering conditions. We investigate this process making use of the quantum-mechanical (QM) model to represent the electronic interactions within the binary collisional formalism. The QM approach is based on the use of the model potential and allows us to describe the main features of the metal surface. It provides a precise description of both one-electron states and surface induced potential. In this work, the approximation is employed to evaluate electron distributions for 100 keV protons impinging grazingly on the Al111 surface. We have found that the realistic representation of the surface included in the QM model introduces substantial changes in the valence emission at low electron energies and intermediate ejection angles. The influence of the surface wake potential on the valence emission probability is also addressed. In order to compare with experiments, we add the contribution coming from atomic inner shells calculated with the field-distorted-wave approximation. Total theoretical results obtained with the QM model are in fairly good agreement with the available experimental data.

Research paper thumbnail of Role of Deprotonation and Cu Adatom Migration in Determining the Reaction Pathways of Oxalic Acid Adsorption on Cu(111)

The Journal of Physical Chemistry C, 2011

Scanning Tunnelling Microscopy (STM), X-ray Photoelectron Spectroscopy (XPS) and first principles... more Scanning Tunnelling Microscopy (STM), X-ray Photoelectron Spectroscopy (XPS) and first principles theoretical calculations have been used to gain insight into the fundamental processes involved in the adsorption and self-assembly of oxalic acid on Cu(111). The experimental data demonstrate that several reaction pathways are involved in the chemisorption of oxalic acid on Cu , one of which leads to deprotonation of the acid into oxalate molecules that form ordered structures on the surface. Theoretical calculations demonstrate that the adsorption of oxalate molecules is not stable on the surface unless copper adatoms are taken into consideration. Coordination with copper adatoms prevents oxalate molecules from getting closer to the substrate, precluding the expected decomposition of oxalate into carbon dioxide.

Research paper thumbnail of Electron emission from metal surfaces by ultra-short pulses

We study electron emission spectra produced by the grazing incidence of ultra-short laser pulses ... more We study electron emission spectra produced by the grazing incidence of ultra-short laser pulses on metal surfaces. To describe this process we introduce a distorted-wave approach, based on a simple description of the solid, which includes the main features of the process, taking into account the contribution of the induced potential. The method is applied to evaluate photoemission from the valence band of Al(111), considering different frequencies and durations of the pulse. The results so obtained are contrasted with the numerical solution to the time-dependent Schrödinger equation (TDSE), finding a very good agreement through the whole energetic range.

Research paper thumbnail of Role of band structure and local-field effects in the low-energy collective electronic excitation spectra of 2<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>H</mml:mi></mml:math>-NbSe<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:...

Physical Review B, Jul 11, 2012

We present a study of the electron dynamics in the layered compound 2H-NbSe 2. First-principles c... more We present a study of the electron dynamics in the layered compound 2H-NbSe 2. First-principles calculations are used to obtain the band structure employed in the evaluation of the loss function with inclusion of local-field (LF) effects. Two different symmetry directions [(100) and (010)] were explored in the hexagonal basal plane. In both cases, a low-energy charge-carrier plasmon (CCP) at ∼1 eV presenting a negative dispersion over a wide momentum transfer range is found, in agreement with recent experimental results [Wezel et al., Phys. Rev. Lett. 107, 176404 (2011)]. On the contrary, in the (001) perpendicular direction, the CCP has negative dispersion at small momenta only, presenting strong positive dispersion at larger momenta. Our calculations reveal that this behavior can be explained without invoking many-body effects, as long as band structure effects are properly included in the evaluation of the excitation spectra. In addition to this CCP mode, we find another one with an arclike oscillating dispersion along the perpendicular direction, as well as the appearance of a CCP replica at high momenta due to LF effects.

Research paper thumbnail of On the stability of the electronic system in transition metal dichalcogenides

Journal of Physics: Condensed Matter, Apr 8, 2016

Research paper thumbnail of Single-molecule enhanced spin-flip detection

arXiv (Cornell University), Nov 2, 2016

We studied the spin-flip excitations of a doubledecker nickelocene molecule (Nc) adsorbed on Cu(1... more We studied the spin-flip excitations of a doubledecker nickelocene molecule (Nc) adsorbed on Cu(100) by means of inelastic tunneling spectroscopy (IETS), X-ray magnetic circular dichroism (XMCD) and density functional theory calculations (DFT). The results show that the molecule preserves its magnetic moment and magnetic anisotropy not only on Cu(100), but also in different metallic environments including the tip apex. Taking advantage of the efficient spin-flip excitation of this molecule, we show how such a molecular functionalized tip boosts the inelastic signal of a surface supported Nc by almost one order of magnitude thanks to a double spin-excitation process.

Research paper thumbnail of Unveiling nickelocene bonding to a noble metal surface

Physical Review B, 2016

The manipulation of a molecular spin state in low-dimensional materials is central to molecular s... more The manipulation of a molecular spin state in low-dimensional materials is central to molecular spintronics. The designs of hybrid devices incorporating magnetic metallocenes are very promising in this regard, but are hampered by the lack of data regarding their interaction with a metal. Here, we combine low-temperature scanning tunneling microscopy and density functional theory calculations to investigate a magnetic metallocene at the single-molecule level-nickelocene. We demonstrate that the chemical and electronic structures of nickelocene are preserved upon adsorption on a copper surface. Several bonding configurations to the surface are identified, ranging from the isolated molecule to molecular layers governed by van der Waals interactions.

Research paper thumbnail of Characterization of an oxalic acid layer on Cu(111)

Research paper thumbnail of The densest iron coordination network based on carboxylate ligands

Trabajo presentado al "11th International Conference on Atomically Controlled Surfaces, Inte... more Trabajo presentado al "11th International Conference on Atomically Controlled Surfaces, Interfaces and Nanostructures" celebrado en San Petersburgo del 3 al 7 de octubre del 2011.-- et al.

Research paper thumbnail of N ov 2 01 6 Single-molecule enhanced spin-flip detection

We studied the spin-flip excitations of a double-decker nickelocene molecule (Nc) adsorbed on Cu(... more We studied the spin-flip excitations of a double-decker nickelocene molecule (Nc) adsorbed on Cu(100) by means of inelastic tunneling spectroscopy (IETS), X-ray magnetic circular dichroism (XMCD) and density functional theory calculations (DFT). The results show that the molecule preserves its magnetic moment and magnetic anisotropy not only on Cu(100), but also in different metallic environments including the tip apex. Taking advantage of the efficient spin-flip excitation of this molecule, we show how such a molecular functionalized tip boosts the inelastic signal of a surface supported Nc by almost one order of magnitude thanks to a double spin-excitation process.

Research paper thumbnail of On the stability of the electronic system in transition metal dichalcogenides

Journal of Physics: Condensed Matter, 2016

Research paper thumbnail of Modeling Ferro- and Antiferromagnetic Interactions in Metal–Organic Coordination Networks

The Journal of Physical Chemistry C, 2014

Magnetization curves of two rectangular metal-organic coordination networks formed by the organic... more Magnetization curves of two rectangular metal-organic coordination networks formed by the organic ligand TCNQ (7,7,8,8-tetracyanoquinodimethane) and two different (Mn and Ni) 3d transition metal atoms [M(3d)] show marked differences that are explained using first principles density functional theory and model calculations. We find that the existence of a weakly dispersive hybrid band with M(3d) and TCNQ character crossing the Fermi level is determinant for the appearance of ferromagnetic coupling between metal centers, as it is the case of the metallic system Ni-TCNQ but not of the insulating system Mn-TCNQ. The spin magnetic moment localized at the Ni atoms induces a significant spin polarization in the organic molecule; the corresponding spin density being delocalized along the whole system. The exchange interaction between localized spins at Ni centers and the itinerant spin density is ferromagnetic. Based on two different model Hamiltonians, we estimate the strength of exchange couplings between magnetic atoms for both Ni-and Mn-TCNQ networks that results in weak ferromagnetic and very weak antiferromagnetic correlations for Ni-and Mn-TCNQ networks, respectively.

Research paper thumbnail of Influence of the surface band structure on electron emission spectra from metal surfaces

Physical Review B, 2014

Electron distributions produced by grazing impact of fast protons on Mg(0001), Cu(111), Ag(111) a... more Electron distributions produced by grazing impact of fast protons on Mg(0001), Cu(111), Ag(111) and Au(111) surfaces are investigated, focusing on the effects of the electronic band structure. The process is described within the Band-Structure-Based approximation, which is a perturbative method that includes an accurate representation of the electron-surface interaction, incorporating information of the electronic band structure of the solid. For all the studied surfaces, the presence of partially occupied surface electronic states produces noticeable structures in double differentialenergy-and angle-resolved-electron emission probabilities from the valence band. These structures remain visible in electron emission spectra after adding contributions coming from core electrons, which might make it possible their experimental detection.

Research paper thumbnail of Interaction of ultrashort laser pulses with metal surfaces: Impulsive jellium-Volkov approximation versus the solution of the time-dependent Schrödinger equation

Physical Review A, 2007

Electron emission coming from the valence band of metal surfaces due to grazing incidence of high... more Electron emission coming from the valence band of metal surfaces due to grazing incidence of highfrequency ultrashort laser pulses is studied. We introduce a distorted-wave method, named impulsive jellium-Volkov ͑IJV͒ approximation, in which the surface is represented by the jellium model while the interaction with the laser field is described by means of the Volkov phase. With the purpose of examining the proposed approach, we compare IJV results with values derived from the numerical solution of the corresponding time-dependent Schrödinger equation ͑TDSE͒. For Al͑111͒ surfaces, double and single differential probability spectra are calculated considering different durations of the laser pulse. Very good agreement between IJV and TDSE results was found. The total probability dependence on the intensity and carrier-envelope phase of the pulse is also investigated.

Research paper thumbnail of Study of the induced potential produced by ultrashort pulses on metal surfaces

Journal of the Optical Society of America B, 2009

The influence of the induced potential on photoelectron emission from metal surfaces is studied f... more The influence of the induced potential on photoelectron emission from metal surfaces is studied for grazing incidence of ultra short laser pulses. To describe this process we introduce a distorted wave-method, the Surface Jellium-Volkov approach, which includes the perturbation on the emitted electron produced by both the laser and the induced fields. The method is applied to an Al(111) surface contrasting the results with the numerical solution to the time-dependent Schrödinger equation (TDSE). We found that SJV approach reproduces well the main features of emission spectra, accounting properly for effects originated by the induced potential.

Research paper thumbnail of Dimensionality reduction to improve search time and memory footprint in content-retrieval tasks: Application to semiconductor inspection images

Advances in Industrial and Manufacturing Engineering

Research paper thumbnail of Efficient Spin-Flip Excitation of a Nickelocene Molecule

Research paper thumbnail of Band-structure-based collisional model for electronic excitations in ion-surface collisions

Physical Review A, 2005

Energy loss per unit path in grazing collisions with metal surfaces is studied by using the colli... more Energy loss per unit path in grazing collisions with metal surfaces is studied by using the collisional and dielectric formalisms. Within both theories we make use of the band-structure-based ͑BSB͒ model to represent the surface interaction. The BSB approach is based on a model potential and provides a precise description of the one-electron states and the surface-induced potential. The method is applied to evaluate the energy lost by 100 keV protons impinging on aluminum surfaces at glancing angles. We found that when the realistic BSB description of the surface is used, the energy loss obtained from the collisional formalism agrees with the dielectric one, which includes not only binary but also plasmon excitations. The distance-dependent stopping power derived from the BSB model is in good agreement with available experimental data. We have also investigated the influence of the surface band structure in collisions with the Al͑100͒ surface. Surface-state contributions to the energy loss and electron emission probability are analyzed.

Research paper thumbnail of Photoelectron emission from metal surfaces by ultrashort laser pulses

Physical Review A, 2006

Electron emission from metal surfaces produced by short laser pulses is studied within the framew... more Electron emission from metal surfaces produced by short laser pulses is studied within the framework of the distorted-wave formulation. The proposed approach, named surface-Volkov ͑SV͒ approximation, makes use of the band-structure based ͑BSB͒ model and the Volkov phase to describe the interaction of the emitted electron with the surface and the external electric field, respectively. The BSB model provides a realistic representation of the surface, based on a model potential that includes the main features of the surface band structure. The SV method is applied to evaluate the photoelectron emission from the valence band of Al͑111͒. Angular and energy distributions are investigated for different parameters of the laser pulse, keeping in all cases the carrier frequency larger than the plasmon one.

Research paper thumbnail of Quantum-mechanical model for valence-electron emission from metal surfaces

Physical Review A

Electron emission from the conduction band of metal surfaces is studied under grazing scattering ... more Electron emission from the conduction band of metal surfaces is studied under grazing scattering conditions. We investigate this process making use of the quantum-mechanical (QM) model to represent the electronic interactions within the binary collisional formalism. The QM approach is based on the use of the model potential and allows us to describe the main features of the metal surface. It provides a precise description of both one-electron states and surface induced potential. In this work, the approximation is employed to evaluate electron distributions for 100 keV protons impinging grazingly on the Al(111) surface. We have found that the realistic representation of the surface included in the QM model introduces substantial changes in the valence emission at low electron energies and intermediate ejection angles. The influence of the surface wake potential on the valence emission probability is also addressed. In order to compare with experiments, we add the contribution coming...

Research paper thumbnail of Quantum-mechanical model for valence-electron emission from metal surfaces

Electron emission from the conduction band of metal surfaces is studied under grazing scattering ... more Electron emission from the conduction band of metal surfaces is studied under grazing scattering conditions. We investigate this process making use of the quantum-mechanical (QM) model to represent the electronic interactions within the binary collisional formalism. The QM approach is based on the use of the model potential and allows us to describe the main features of the metal surface. It provides a precise description of both one-electron states and surface induced potential. In this work, the approximation is employed to evaluate electron distributions for 100 keV protons impinging grazingly on the Al111 surface. We have found that the realistic representation of the surface included in the QM model introduces substantial changes in the valence emission at low electron energies and intermediate ejection angles. The influence of the surface wake potential on the valence emission probability is also addressed. In order to compare with experiments, we add the contribution coming from atomic inner shells calculated with the field-distorted-wave approximation. Total theoretical results obtained with the QM model are in fairly good agreement with the available experimental data.

Research paper thumbnail of Role of Deprotonation and Cu Adatom Migration in Determining the Reaction Pathways of Oxalic Acid Adsorption on Cu(111)

The Journal of Physical Chemistry C, 2011

Scanning Tunnelling Microscopy (STM), X-ray Photoelectron Spectroscopy (XPS) and first principles... more Scanning Tunnelling Microscopy (STM), X-ray Photoelectron Spectroscopy (XPS) and first principles theoretical calculations have been used to gain insight into the fundamental processes involved in the adsorption and self-assembly of oxalic acid on Cu(111). The experimental data demonstrate that several reaction pathways are involved in the chemisorption of oxalic acid on Cu , one of which leads to deprotonation of the acid into oxalate molecules that form ordered structures on the surface. Theoretical calculations demonstrate that the adsorption of oxalate molecules is not stable on the surface unless copper adatoms are taken into consideration. Coordination with copper adatoms prevents oxalate molecules from getting closer to the substrate, precluding the expected decomposition of oxalate into carbon dioxide.