Abstract We propose a new, general method for obtaining closed form solutions of electrostatic re... more Abstract We propose a new, general method for obtaining closed form solutions of electrostatic response problems in solid bodies of arbitrary shape. The scheme is simple enough to be applied to problems with complicated geometries, yet it should be sufficiently reliable for most purposes. It is shown that its formulation in terms of boson pseudomodes provides a convenient generalization of a method proposed by Overhauser to treat electron correlation in metals. Explicit expressions are given for the image interaction between a point charge and a plane or spherical surface, and for the screening energies and the screened electric fields of impurities in size quantized metals. Several implications in the physical and chemical properties of small metal particles are briefly discussed. Quantum size effects are included by means of a suitable dielectric function, including quantum size, exchange and correlation effects, and are shown to be very significant when the particle radius is of the order of a few tens of angstroms.
Valence holes can react to various elementary excitations, such as plasmons and phonons, causing ... more Valence holes can react to various elementary excitations, such as plasmons and phonons, causing them to relax coherently in the final states of electron spectroscopies. This can produce interesting effects on the lineshapes. Here the photoemission spectra of a chemisorbate or an impurity are discussed in the framework of a model that explicitly deals with the dynamics of two different boson modes. The exact solution is given and leads to the conclusion that coherence effects are important when the two excitations give comparable contributions to the relaxation energy. The dynamical effects due to the plasmons end to enhance the vibrational structures.
SummaryTo understand the electronic processes that occur during desorption, we must allow simulta... more SummaryTo understand the electronic processes that occur during desorption, we must allow simultaneously for the intrinsic nonadiabatic character of electron states and for correlation-induced features like two-hole resonances. A recently proposed theory describes the Menzel-Gomer-Redhead and Knotek-Fiebelman mechanisms on equal footing and reveals a complex interplay of electronic and kinematic effects on the ion yield. Here, I wish to show how in the same scheme we can also obtain the yield of ions that have suffered (partial or total) re-neutralization in the course of desorption. Closed-form expressions for the relevant escape probabilities are given in terms of one-hole and two-hole Green’s functions. The surface molecule limit of the theory is worked out in detail assuming that the hopping parameters decay exponentially in time during desorption. It is shown that, in general, when a given species can be desorbed by different mechanisms, we can discriminate them experimentally by the energy and angular dependence of the yield.RiassuntoPer comprendere i processi elettronici che avvengono nel desorbimento, dobbiamo tener conto che gli stati hanno un carattere intrinsecamente non adiabatico. Allo stesso tempo, occorre includere gli effetti di correlazione, come, ad esempio, le risonanze a due buche. Una teoria recente consente una descrizione unificata dei meccanismi di Menzel-Gomer-Redhead e di Knotek-Feibelman; essa mostra che effetti elettronici ed effetti cinematici concorrono in modo complesso a determinare la resa di ioni. Qui si vuol far vedere come tale teoria consenta di ottenere la resa anche per le specie che subiscono una rineutralizzazione parziale o totale nel corso del desorbimento. Le probabilità che lo ione desorba nei vari stati di carica sono espresse in forma chiusa in termini delle funzioni di Green a una e due buche. Il limite della molecola superficiale è risolto in dettaglio nel caso in cui i parametri di salto decadono esponenzialmente nel tempo durante il desorbimento. Si trova che, quando diversi meccanismi portano al desorbimento di una stessa specie, è generalmente possibile distinguerli per le diverse dipendenze dall’energia cinetica e dagli angoli.РезюмеЧтобы понять электронные процессы, происходящие при десорбции, мы должны одновременно учитывать внутренний неадиабатический характер электронных состояний и особенности, подобные двухдырочным резонансам. Недавно предложенная теория описывает механизмы Менцеля-Гомера-Редхеда и Нотека-Фейбелмана и обнаруживает комплексное влияние электронного и кинематического эффектов на выход ионов. В рамках этой схемы мы хотим показать, как можно получить выход ионов, которые испытывают (частичную и полную) ренейтрализацию в процессе десорбции. Приводятся замкнутые выражения для соответствующих вероятностей вылета в терминах одно-дырочных и двух-дырочных функций Грина. Разрабатывается предел теории для молекулы на поверхности, предполагая, что параметры «перепыгивания» экспоненциально затухают во времени в процессе десорбции. Показывается, что, когда заданный тип частиц может быть десорбирован за счет различных механизмов, мы можем дискриминировать их экспериментально, используя энергетическую и утловую зависимости выхода.
... terest. ' Changes of the energy position... more ... terest. ' Changes of the energy position and width of the structures are observed in the valenceband, core lev-els, and conduction states of the metal particles as a func-tion of their size. These changes have been discussed in terms of initial-and/or final-state effects due to ...
Abstract The usual approach to second harmonic generation (SHG) is based on low-order pertubation... more Abstract The usual approach to second harmonic generation (SHG) is based on low-order pertubation theory and neglects the changes in the electronic states that are induced by the exciting beam. To see whathappens in this approximation fails we propose a new formalism, based on the method of excitation amplitudes, to set up a theory of the SHG response and other inelastic light scattering phenomena. We develop the quantum theory in the dipole approximation and show that the inclusion of electron-photon coupling to all others leads to new features. Strong exciting fields produce a nonnegligible SHG response in highly polarisable centro-symmetric systems, and the emitted spectrum shows a dynamical Stark effect.
Let Â=† be an observable operator with a complete set of eigenstates |ϕ n 〉 with eigenvalues α n... more Let Â=† be an observable operator with a complete set of eigenstates |ϕ n 〉 with eigenvalues α n (n=0, 1, 2,...). A generic state is given by $$\left. {|\psi } \right\rangle = \left. {N(3|{\psi _1}} \right\rangle \left. { - 4i|{\psi _2}} \right\rangle )$$ where |ψ1〉,|ψ2〉 are orthonormal. Find N and the probability P 4 that a measurement of  yields α4. What does it happen in case of degeneracy? Specialize these calculations to the case |ϕ n 〉=|ψ n 〉.
SummaryWhen a chemisorbed atom undergoes a CVV Auger transition, the surface polarization modes r... more SummaryWhen a chemisorbed atom undergoes a CVV Auger transition, the surface polarization modes respond no faster than the surface plasmon frequency. Hence we must expect deviations from the current description of CVV line shapes that assumes instantaneous screening. Here we propose an extended theory than includes dynamicalscreening effects. Our description applies to systems that have filled valence bands in the ground states. The absence of a translational symmetry implies a model Hamiltonian that is different and more involved than the one appropriate for homogeneous solids. The exact solution leads to a complex phenomenology that we illustrate by selected examples.RiassuntoQuando una transizione Auger CVV ha luogo in un atomo chemisorbito, i modi di polarizzazione rispondono su frequenze non superiori a quella del plasmone di superficie. Pertanto ci dobbiamo aspettare deviazioni dalla teoria usuale delle forme di riga CVV, che presuppone uno schermo istantaneo. Qui si propone una teoria generalizzata che include effetti di schermo dinamico ed è applicabile a sistemi che hanno bande di valenza interamente occupate nello stato fondamentale. Poichè, manca la simmetria traslazionale, l’hamiltoniana modello è piú complicata di quella adatta a descrivere solidi omogenei. La soluzione, esatta conduce ad una fenomenologia complessa e noi abbiamo selezionato una serie di esempi per illustrarla.РезюмеКогда хемисорбированный атом претерпевает CVV Оже-переход, поверхностные поляризационные моды реагируют не быстрее, чем поверхностная плазмонная частота. Следовательно, мы должны ожидать отклоненнй от теории, описывающей форму CVV линий, в которой предполагается мгновенное экранирование. Мы предлагаем обобщенную теорию, чтобы включить эффекты динамического экранирования. Предлож енное нами олисание применяется к системе, которая имеет заполненные валентные зоны в основных состояниях Отсутствие трансляционной симметрии подразумевает модельный Гамильтониан, который является более сложным, чем Гамильтониан для однородных твердых тел. Точное решение приводит к сложной феноменологии, которую мы иллюстрируем на частных на частных примераш.
Abstract We propose a new, general method for obtaining closed form solutions of electrostatic re... more Abstract We propose a new, general method for obtaining closed form solutions of electrostatic response problems in solid bodies of arbitrary shape. The scheme is simple enough to be applied to problems with complicated geometries, yet it should be sufficiently reliable for most purposes. It is shown that its formulation in terms of boson pseudomodes provides a convenient generalization of a method proposed by Overhauser to treat electron correlation in metals. Explicit expressions are given for the image interaction between a point charge and a plane or spherical surface, and for the screening energies and the screened electric fields of impurities in size quantized metals. Several implications in the physical and chemical properties of small metal particles are briefly discussed. Quantum size effects are included by means of a suitable dielectric function, including quantum size, exchange and correlation effects, and are shown to be very significant when the particle radius is of the order of a few tens of angstroms.
Valence holes can react to various elementary excitations, such as plasmons and phonons, causing ... more Valence holes can react to various elementary excitations, such as plasmons and phonons, causing them to relax coherently in the final states of electron spectroscopies. This can produce interesting effects on the lineshapes. Here the photoemission spectra of a chemisorbate or an impurity are discussed in the framework of a model that explicitly deals with the dynamics of two different boson modes. The exact solution is given and leads to the conclusion that coherence effects are important when the two excitations give comparable contributions to the relaxation energy. The dynamical effects due to the plasmons end to enhance the vibrational structures.
SummaryTo understand the electronic processes that occur during desorption, we must allow simulta... more SummaryTo understand the electronic processes that occur during desorption, we must allow simultaneously for the intrinsic nonadiabatic character of electron states and for correlation-induced features like two-hole resonances. A recently proposed theory describes the Menzel-Gomer-Redhead and Knotek-Fiebelman mechanisms on equal footing and reveals a complex interplay of electronic and kinematic effects on the ion yield. Here, I wish to show how in the same scheme we can also obtain the yield of ions that have suffered (partial or total) re-neutralization in the course of desorption. Closed-form expressions for the relevant escape probabilities are given in terms of one-hole and two-hole Green’s functions. The surface molecule limit of the theory is worked out in detail assuming that the hopping parameters decay exponentially in time during desorption. It is shown that, in general, when a given species can be desorbed by different mechanisms, we can discriminate them experimentally by the energy and angular dependence of the yield.RiassuntoPer comprendere i processi elettronici che avvengono nel desorbimento, dobbiamo tener conto che gli stati hanno un carattere intrinsecamente non adiabatico. Allo stesso tempo, occorre includere gli effetti di correlazione, come, ad esempio, le risonanze a due buche. Una teoria recente consente una descrizione unificata dei meccanismi di Menzel-Gomer-Redhead e di Knotek-Feibelman; essa mostra che effetti elettronici ed effetti cinematici concorrono in modo complesso a determinare la resa di ioni. Qui si vuol far vedere come tale teoria consenta di ottenere la resa anche per le specie che subiscono una rineutralizzazione parziale o totale nel corso del desorbimento. Le probabilità che lo ione desorba nei vari stati di carica sono espresse in forma chiusa in termini delle funzioni di Green a una e due buche. Il limite della molecola superficiale è risolto in dettaglio nel caso in cui i parametri di salto decadono esponenzialmente nel tempo durante il desorbimento. Si trova che, quando diversi meccanismi portano al desorbimento di una stessa specie, è generalmente possibile distinguerli per le diverse dipendenze dall’energia cinetica e dagli angoli.РезюмеЧтобы понять электронные процессы, происходящие при десорбции, мы должны одновременно учитывать внутренний неадиабатический характер электронных состояний и особенности, подобные двухдырочным резонансам. Недавно предложенная теория описывает механизмы Менцеля-Гомера-Редхеда и Нотека-Фейбелмана и обнаруживает комплексное влияние электронного и кинематического эффектов на выход ионов. В рамках этой схемы мы хотим показать, как можно получить выход ионов, которые испытывают (частичную и полную) ренейтрализацию в процессе десорбции. Приводятся замкнутые выражения для соответствующих вероятностей вылета в терминах одно-дырочных и двух-дырочных функций Грина. Разрабатывается предел теории для молекулы на поверхности, предполагая, что параметры «перепыгивания» экспоненциально затухают во времени в процессе десорбции. Показывается, что, когда заданный тип частиц может быть десорбирован за счет различных механизмов, мы можем дискриминировать их экспериментально, используя энергетическую и утловую зависимости выхода.
... terest. ' Changes of the energy position... more ... terest. ' Changes of the energy position and width of the structures are observed in the valenceband, core lev-els, and conduction states of the metal particles as a func-tion of their size. These changes have been discussed in terms of initial-and/or final-state effects due to ...
Abstract The usual approach to second harmonic generation (SHG) is based on low-order pertubation... more Abstract The usual approach to second harmonic generation (SHG) is based on low-order pertubation theory and neglects the changes in the electronic states that are induced by the exciting beam. To see whathappens in this approximation fails we propose a new formalism, based on the method of excitation amplitudes, to set up a theory of the SHG response and other inelastic light scattering phenomena. We develop the quantum theory in the dipole approximation and show that the inclusion of electron-photon coupling to all others leads to new features. Strong exciting fields produce a nonnegligible SHG response in highly polarisable centro-symmetric systems, and the emitted spectrum shows a dynamical Stark effect.
Let Â=† be an observable operator with a complete set of eigenstates |ϕ n 〉 with eigenvalues α n... more Let Â=† be an observable operator with a complete set of eigenstates |ϕ n 〉 with eigenvalues α n (n=0, 1, 2,...). A generic state is given by $$\left. {|\psi } \right\rangle = \left. {N(3|{\psi _1}} \right\rangle \left. { - 4i|{\psi _2}} \right\rangle )$$ where |ψ1〉,|ψ2〉 are orthonormal. Find N and the probability P 4 that a measurement of  yields α4. What does it happen in case of degeneracy? Specialize these calculations to the case |ϕ n 〉=|ψ n 〉.
SummaryWhen a chemisorbed atom undergoes a CVV Auger transition, the surface polarization modes r... more SummaryWhen a chemisorbed atom undergoes a CVV Auger transition, the surface polarization modes respond no faster than the surface plasmon frequency. Hence we must expect deviations from the current description of CVV line shapes that assumes instantaneous screening. Here we propose an extended theory than includes dynamicalscreening effects. Our description applies to systems that have filled valence bands in the ground states. The absence of a translational symmetry implies a model Hamiltonian that is different and more involved than the one appropriate for homogeneous solids. The exact solution leads to a complex phenomenology that we illustrate by selected examples.RiassuntoQuando una transizione Auger CVV ha luogo in un atomo chemisorbito, i modi di polarizzazione rispondono su frequenze non superiori a quella del plasmone di superficie. Pertanto ci dobbiamo aspettare deviazioni dalla teoria usuale delle forme di riga CVV, che presuppone uno schermo istantaneo. Qui si propone una teoria generalizzata che include effetti di schermo dinamico ed è applicabile a sistemi che hanno bande di valenza interamente occupate nello stato fondamentale. Poichè, manca la simmetria traslazionale, l’hamiltoniana modello è piú complicata di quella adatta a descrivere solidi omogenei. La soluzione, esatta conduce ad una fenomenologia complessa e noi abbiamo selezionato una serie di esempi per illustrarla.РезюмеКогда хемисорбированный атом претерпевает CVV Оже-переход, поверхностные поляризационные моды реагируют не быстрее, чем поверхностная плазмонная частота. Следовательно, мы должны ожидать отклоненнй от теории, описывающей форму CVV линий, в которой предполагается мгновенное экранирование. Мы предлагаем обобщенную теорию, чтобы включить эффекты динамического экранирования. Предлож енное нами олисание применяется к системе, которая имеет заполненные валентные зоны в основных состояниях Отсутствие трансляционной симметрии подразумевает модельный Гамильтониан, который является более сложным, чем Гамильтониан для однородных твердых тел. Точное решение приводит к сложной феноменологии, которую мы иллюстрируем на частных на частных примераш.
Uploads