Rationale for plasmonically assisted electron emission model
Since the advent of modern spectroscopic techniques and the development of quantum many-body theory a great deal of attention and work have been focused on the various aspects of mutual interactions of electromagnetic waves, plasmonic fields and electrons in inhomogeneously structured dielectric media. The plasmonic phenomena arising from the interplay of these interactions have aroused considerable and unabated interest, partly because of their potential roles in communication and computing
Model description of excitation of electron–plasmon system by EM field
Symmetry selection rules do not permit direct excitation of longitudinal bulk plasmons in metals by purely transversely polarized EM fields. Therefore, the intriguing “non-Einsteinian” photoemission modes described in the Introduction call for interpretations going beyond the sole effect of electron excitation by dielectrically screened EM fields , , ,  which oscillate with the frequencies of the applied external fields. We introduce a novel paradigm which involves real plasmon
Perturbative treatment of bulk plasmon-assisted electron emission from metals
Formation and structure of plasmonic coherent states (9) which can drive plasmoemission are controlled by the saturated mode occupation amplitudes . As they stand, these amplitudes are -resolved and electronic band (-band) integrated quantities retrievable from expressions (23) and (28) of Ref. . As such they do not provide much insight into the dynamics of intra- and interband electronic transitions giving rise to plasmon excitations. Hence, in the following we shall prefer to
Model description of surface plasmon-induced electron excitations at metal surfaces
Low index surfaces of some metals may exhibit surface projected band gaps. This means that there are no electrons with energies within the gap that can propagate normal to the surface. The effective one-electron potential at such surfaces can support the set of quasi-two-dimensional (Q2D) surface state (SS) and image potential state (IP) bands. Localization of SS and IP electrons in the direction perpendicular to the surface is only few atomic radii over the image potential well whereas their
Quantum formulation in the scattering boundary conditions
The use of the velocity gauge in the calculations of transition amplitudes usually provides faster converging results. Hence, we rewrite (43), (44) starting from integral representation of the evolution operator to obtain the SBC limit of the transition amplitude in either picture Here and consistent with (42) vanishes in the remote past
Depending on the boundary conditions specific to a particular problem, the Volkov ansatz-derived electron states may participate in emission or scattering processes as either initial, intermediate or final states , , , , , , . The initial field-dressed band states are conventionally termed Floquet or Bloch-Floquet states whereas the final outgoing field-dressed electron states are designated Volkov states , , . In the present problem of electron
Discussion of plasmoemission from surface Floquet bands on (111)
Signatures of Floquet sidebands in plasmoemission rates predicted by the RHS of expression (84) largely depend on two factors. The first is related to the values of generalized Bessel functions with parametric variables , and in relation to of the interacting electron-SP system. The second one pertains to the overall magnitude of (90) which determines the weight of each -function in the sum over the Floquet band index in (84). Here we shall separately inspect the high
Pump–probe picture of perturbative and nonperturbative plasmoemission from surface bands
The paradigmatic one-electron pump–probe picture of multiphoton photoemission (PP) is intrinsically perturbative in that it describes amplitudes of th order electron excitations induced by the repeated action of one or more external EM fields . In this scenario absorption of photons can pump an electron over the ladder of real or virtual intermediate states until the absorption of probe photon(s) brings it to the real final outgoing wave state that supports the emission current obeying
Summary and conclusions
In this work we have studied plasmonically induced electron excitation processes that can generate stationary electron currents emanating from metal surfaces. We have exploited a full analogy of these phenomena with standard photoemission to formulate perturbative and nonperturbative pictures of plasmonically induced electron yields. The relevant emission probabilities appear even order in the applied plasmon field, as it should be in the description of externally driven stationary quantities
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
The authors are grateful to M. Reutzel, A. Li and H. Petek for sharing the experimental data on multiphoton photoemission from Ag surfaces. D.N. acknowledges the financial support from the Croatian Science Foundation (Grant No. UIP-2019-04-6869).
Merging model-based two-dimensional principal component analysis
Neurocomputing, Volume 168, 2015, pp. 1198-1206
Two-dimensional Principal Component Analysis (2DPCA) is a prevalent way to represent images with widespread applications. However, its performance will remarkably degenerate when directly using it to online learning and big data analysis. In this paper we present a new constructive approach to merge multiple eigenspaces of 2DPCA for successively adding new observations and then provide an efficient way to solve the projection matrix of incremental 2DPCA. The proposed method takes into account the change of mean of data, which is important for classification, and significantly reduces the computation complexity and storage space. Experimental results on the FERET, AR, and PIE face databases show the efficiency of the proposed method for online learning and big data analysis.
Generations of even-order harmonics from vibrating H2+ and T2+ in the rising and falling parts of the laser field
Chemical Physics, Volume 505, 2018, pp. 47-54
The generations of the even-order harmonics from H2+ and one of its isotope T2+ have been theoretically investigated beyond the Born-Oppenheimer approximation. Normally, the high-order harmonic generation (HHG) only contains odd-order harmonics for the orbital symmetry along the direction of laser polarization. Here, we showed that due to asymmetric harmonic emission (asymmetric half-wave profile), the even-order harmonics can be generated in the rising and the falling part of the laser field. In detail, in the lower initial vibrational state, the even-order harmonics main come from the falling part of the laser field; while as the initial vibrational state increases, the identified even-order harmonics in the falling part of the laser field are decreased; while some other even-order harmonics coming from the rising part of the laser field can be produced. The interesting phenomena have been proved through studying the spatial distributions and the time profiles of the HHG.
What do the two times in two-time correlation functions mean for interpreting tr-ARPES?
Journal of Electron Spectroscopy and Related Phenomena, Volume 251, 2021, Article 147104
Time-resolved angle-resolved photoemission spectroscopy is one of the most powerful pump–probe measurements of materials driven far from equilibrium. Unlike the linear-response regime, where the frequency-dependent response function is independent of time, in a far-from-equilibrium experiment, the response function depends on two times in the time domain. In this work, we describe how one can use time-dependent frequency response functions and how they involve contributions from times that are near to each other. This implies that they should not be thought of as a frequency-dependent response at a single definite time. Instead, the Fourier uncertainty relations show that they involve contributions from ranges of times and must be interpreted in this light. We use this insight to help understand what time-resolved photoemission measurements actually measure.
Coherence and de-coherence in the Time-Resolved ARPES of realistic materials: An ab-initio perspective
Journal of Electron Spectroscopy and Related Phenomena, Volume 257, 2022, Article 147189
Coherence and de-coherence are the most fundamental steps that follow the initial photo-excitation occurring in typical pump-and-probe experiments. Indeed, the initial external laser pulse transfers coherence to the system in terms of creation of multiple electron–hole pairs excitation. The excitation concurs both to the creation of a finite carriers density and to the appearance of induced electromagnetic fields. The two effects, to a very first approximation, can be connected to the simple concepts of populations and oscillations. The dynamics of the system following the initial photo-excitation is, thus, entirely dictated by the interplay between coherence and de-coherence. This interplay and the de-coherence process itself, is due to the correlation effects stimulated by the photo-excitation. Single-particle, like the electron–phonon, and two-particles, like the electron–electron, scattering processes induce a complex dynamics of the electrons that, in turn, makes the description of the correlated and photo-excited system in terms of pure excitonic and/or carriers populations challenging.
1-MCP prevents ultrastructural changes in the organelles of Dendrobium petals that are induced by exogenous ethylene
Plant Physiology and Biochemistry, Volume 200, 2023, Article 107758
Ethylene is a plant hormone that causes flower senescence. Dendrobium flowers are sensitive to ethylene and ethylene can induce premature senescence depending on the cultivar and the ethylene concentration. Dendrobium ‘Lucky Duan’ is one of the most sensitive cultivars to ethylene exposure. Open florets of ‘Lucky Duan’ were subjected to ethylene, 1-MCP, or 1-MCP plus ethylene treatments and compared with an untreated control. Ethylene induced earlier development of color fading, drooping and venation in petals, whereas 1-MCP pre-treatment counteracted these changes. Under light microscopy, epidermal cells and mesophyll parenchyma tissue around the vascular bundles of petals treated with ethylene showed collapsed cells whereas 1-MCP pre-treatment counteracted this collapse. An scanning electron microscopy (SEM) study confirmed clearly that ethylene treatment caused the collapse of mesophyll parenchyma tissue around vascular bundles. Ultrastructural changes were also studied using transmission electron microscopy (TEM) and showed that ethylene treatment induced morphological changes in conjunction with disorganization of the plasma membrane, the nuclei, chromatin, the nucleoli, myelin bodies, multivesicular bodies, and mitochondria including changes in size and number, breakages of membranes, enlargement of intercellular spaces and disintegration. 1-MCP pre-treatment was observed to counter these changes that were induced by ethylene. The role of ethylene-induced ultrastructural changes in the different organelles was apparently associated with membrane damage.
Takotsubo Syndrome Due to Bronchoalveolar Lavage: A Rare Complication
Archivos de Bronconeumología, 2023
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