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Katharina J. Franke - One of the best experts on this subject based on the ideXlab platform.
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Mapping the Perturbation Potential of metallic and dipolar tips in tunneling spectroscopy on MoS 2
Physical Review B, 2019Co-Authors: Nils Krane, Christian Lotze, Nils Bogdanoff, Gaël Reecht, Lei Zhang, Alejandro L. Briseno, Katharina J. FrankeAbstract:Scanning tunneling spectroscopy requires the application of a Potential difference between the sample and a tip. In metal-vacuum-metal junctions, one can safely assume that the Potential is constant along the metallic substrate. Here, we show that the inhomogeneous shape of the electric Potential has to be taken into account when probing spatially extended molecules on a decoupling layer. To this end, oligothiophene-based molecules were deposited on a monolayer of molybdenum disulfide (MoS$_2$) on a Au(111) surface. By probing the delocalized molecular orbital along the thiophene-backbone, we found an apparent intramolecular shift of the positive ion resonance, which can be ascribed to a Perturbation Potential caused by the tip. Using a simple model for the electrostatic landscape, we show that such a Perturbation is caused by the inhomogeneity of the applied bias Potential in the junction and may be further modified by an electric dipole of a functionalized tip. The two effects can be disentangled in tunneling spectra by probing the apparent energy shift of vibronic resonances along the molecular backbone. We suggest that extended molecules on MoS$_2$ can be used as a sensor for the shape of the electrostatic Potential of arbitrary tips.
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mapping the Perturbation Potential of metallic and dipolar tips in tunneling spectroscopy on mos 2
Physical Review B, 2019Co-Authors: Nils Krane, Christian Lotze, Nils Bogdanoff, Gaël Reecht, Lei Zhang, Alejandro L. Briseno, Katharina J. FrankeAbstract:Scanning tunneling spectroscopy is a powerful tool to investigate the electronic structure of molecules on surfaces. The technique requires the application of a Potential difference between sample and tip. Whereas the Potential is constant along a metallic substrate, it is inhomogeneous along the surface of an insulating layer such as MoS${}_{2}$. The authors now show that the inhomogeneous shape of the electric Potential and dipole contributions perturb the electronic states of the molecules leading to an apparent shift of the electronic states along extended molecules.
Jiaqing Xue - One of the best experts on this subject based on the ideXlab platform.
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Variations in atmospheric Perturbation Potential energy associated with the South China Sea summer monsoon
Climate Dynamics, 2019Co-Authors: Yazhou Zhang, Qiuyun Wang, Jiaqing XueAbstract:This study investigates the energy conversion processes and their relation to convection (circulation) during the South China Sea summer monsoon (SCSSM) years from the viewpoint of atmospheric Perturbation Potential energy (PPE). An atmospheric PPE dipole pattern associated with the SCSSM develops over the western North Pacific (WNP) and southern Maritime Continent (SMC) in the boreal summer, serving as a link between the SCSSM and diabatic heating. Actually, the conversion between the energy variations and the convection over the WNP is distinctly different with that over the SMC. The precipitation leads the PPE over the WNP, while similar situation is reversed over the SMC. During strong SCSSM years, the higher PPE over the WNP, controlled primarily by the latent heat released from condensation related to surplus precipitation, is corresponding to the negative energy conversion ( $$ \text{C}_{k} $$ ) over there. This indicates that more PPE is converted to Perturbation kinetic energy and further intensifying ascending motion over the WNP. Consequently, the descending movement reduces the PPE and is corresponding to positive $$ \text{C}_{k} $$ over the SMC, suggesting that the less PPE converts into the Perturbation kinetic energy and in turn favors the descending movement and deficit precipitation there. The enhanced southwesterly induced by this SCSSM Hadley circulation, superimposed on the mean southwesterly wind, further favors the intensification of the SCSSM, implying that the SCSSM can maintain development through the positive convection–PPE–circulation feedback.
Li Jian - One of the best experts on this subject based on the ideXlab platform.
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Theory on layer Perturbation Potential energy and its application:a case study on annual variation of the South China Sea summer monsoon
Chinese Journal of Geophysics, 2013Co-Authors: Li JianAbstract:Based on the theory of Perturbation Potential Energy(PPE),at the issue of energy transform at any isobaric surface in local circulation,the concept of Layer Perturbation Potential energy(denoted as the LPPE) is presented.The first-order moment term of LPPE(denoted as LPPE1) is positive over the tropics and negative over high-latitude regions in the low and middle troposphere.It is positive over high-latitude of North American at 200hPa,but is positive over the high-latitude and negative over the tropics at 100 hPa and higher isobaric surface.The distributions of the LPPE1 in the winter hemisphere is quite similar to that of the annual mean,and the LPPE1 is featured by maxima over the Continent in the summer hemisphere.Locally,as the LPPE1 is superior to the second-order(denoted as LPPE2) and high-order ones in order of magnitude,the distributions of the LPPE are quite similar to the LPPE1.The analyses show that there is a significant negative correlation between the LPPE and kinetic energy at 850hPa over the South China Sea Summer Monsoon(denoted as SCSSM) region.There is a significant positive correlation between the SCSSM index(denoted as SCSSMI) and the out-of-phase pattern of LPPE1 in the prior spring which is a substantial relation,the later could be taken as an indicator of the SCSSM variation.The spring sea surface temperature anomalies(denoted as SSTA) over Indian Ocean are closely related to the out-of-phase relationship between anomalies in the tropical oceans and those in the extra-tropical Asian Continent of LPPE1 in spring and JJAS.The out-of-phase relationship of LPPE1 and coherent distribution of Kinetic Energy over SCSSM region are the dominant pattern of their coupled modes,westerly wind increases over the SCSSM region while Kinetic Energy increases,further influences the SCSSM.
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Theory on Perturbation Potential Energy and Its Applications—Concept,Expression and Spatio-Temporal Structures of Perturbation Potential Energy
Chinese Journal of Atmospheric Sciences, 2006Co-Authors: Li JianAbstract:On the issue of energy transform in local circulation,the theory on Perturbation Potential energy(PPE) and its application are investigated in a series of researches.First of all,a new concept on perturbed Potential energy is presented in part I of the series.The PPE may be partitioned into the atmospheric section(denoted as the PPE) and the surface section(termed the surface PPE),and mathematical expressions of every-order moment term of the PPE are given.Combined with data analyses,it can be pointed out that all of higher order moment terms of the PPE than two order are small in magnitude and may be omitted in comparison with the first and second order moment terms of the PPE,and that the second-order moment term of the PPE averaged over the globe just is equal to traditional available Potential energy(APE),but there is evident difference in physical sense between them.Based on the NCEP/NCAR reanalysis data,the spatio-temporal structures of the PPE and their linkages with the atmospheric kinetic energy(AKE) are examined.The first-order moment term of the PPE is positive over the tropics and negative over high-latitude regions,whereas the second-moment term of the PPE is featured by maxima over both the tropics and high latitudes and by minima over both the subtropics and middle-latitude regions,that is to say,which is featured by three peaks and two valleys in the meridional direction.Locally,as the first-order moment term of the PPE is superior to the second-order one in order of magnitude,the distributions of the PPE are quite similar to the first-order moment term.In the vertical direction,the PPE mostly exists in the low troposphere and quickly decreases in magnitude as height increases,which can be omitted above 50 hPa level.On the other hand,the PPE is characterized clearly by evident seasonal variations and is larger in the winter hemisphere than in the summer hemisphere over high-latitude regions.The amplitudes of seasonal variations for the first-order moment term of the PPE averaged in the Southern or Northern Hemispheres are appropriately twenty times larger than those of the corresponding second-order moment term.Against the seasons,the troughs and ridges of the PPE stationary waves show significant zonal movements in the Northern Hemisphere,however,those in the Southern Hemisphere only show the changes in amplitudes.The analyses further show that on local-regional scales,there exists a significant negative correlation between the AKE and the first-order moment PPE on seasonal march,but the relationship between the AKE and the second-order moment term is uncertain.However,on global or hemispheric scale,the ratios of the AKE to the second-order moment term of the PPE are basically invariable and about 20%.Furthermore,the analyses on the spatio-temporal structures of the total AKE exhibit some new results different from those of the previous researches.Moreover,some further relative problems explored by using the concept and theory of the PPE,such as analysis of energy budget in local circulation,role of the surface PPE,and their applications to the studies on atmospheric general circulation variability,will be given in the future papers of the series.
Nils Krane - One of the best experts on this subject based on the ideXlab platform.
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Mapping the Perturbation Potential of metallic and dipolar tips in tunneling spectroscopy on MoS 2
Physical Review B, 2019Co-Authors: Nils Krane, Christian Lotze, Nils Bogdanoff, Gaël Reecht, Lei Zhang, Alejandro L. Briseno, Katharina J. FrankeAbstract:Scanning tunneling spectroscopy requires the application of a Potential difference between the sample and a tip. In metal-vacuum-metal junctions, one can safely assume that the Potential is constant along the metallic substrate. Here, we show that the inhomogeneous shape of the electric Potential has to be taken into account when probing spatially extended molecules on a decoupling layer. To this end, oligothiophene-based molecules were deposited on a monolayer of molybdenum disulfide (MoS$_2$) on a Au(111) surface. By probing the delocalized molecular orbital along the thiophene-backbone, we found an apparent intramolecular shift of the positive ion resonance, which can be ascribed to a Perturbation Potential caused by the tip. Using a simple model for the electrostatic landscape, we show that such a Perturbation is caused by the inhomogeneity of the applied bias Potential in the junction and may be further modified by an electric dipole of a functionalized tip. The two effects can be disentangled in tunneling spectra by probing the apparent energy shift of vibronic resonances along the molecular backbone. We suggest that extended molecules on MoS$_2$ can be used as a sensor for the shape of the electrostatic Potential of arbitrary tips.
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mapping the Perturbation Potential of metallic and dipolar tips in tunneling spectroscopy on mos 2
Physical Review B, 2019Co-Authors: Nils Krane, Christian Lotze, Nils Bogdanoff, Gaël Reecht, Lei Zhang, Alejandro L. Briseno, Katharina J. FrankeAbstract:Scanning tunneling spectroscopy is a powerful tool to investigate the electronic structure of molecules on surfaces. The technique requires the application of a Potential difference between sample and tip. Whereas the Potential is constant along a metallic substrate, it is inhomogeneous along the surface of an insulating layer such as MoS${}_{2}$. The authors now show that the inhomogeneous shape of the electric Potential and dipole contributions perturb the electronic states of the molecules leading to an apparent shift of the electronic states along extended molecules.
Guo Yan - One of the best experts on this subject based on the ideXlab platform.
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Governing Equations of Atmospheric Layer Perturbation Potential Energy and Its Applications-Energy Budget of the South China Sea Summer Monsoon Activity
Chinese Journal of Atmospheric Sciences, 2012Co-Authors: Wang Lei, Li Jianping, Guo YanAbstract:On the issue of energy transform in local circulation,the governing equations of layer Perturbation Potential energy order 1(denoted as LPPE1) and kinetic energy(KE) are derived and the spatial distribution and seasonal variation of the related terms are investigated,the energy budgets of South China Sea summer monsoon(SCSSM) activity in different phases are studied.At 850 hPa level,the sources of LPPE1 locate in the Intertropical Convergence Zone,most monsoon regions,and storm track regions,while the sinks of LPPE1 locate in the subtropical eastern oceans and high latitudes.In general,the strong sources(sinks) of LPPE1 coincide with the ridges(troughs) in its zonal departure distribution.The conversion term(CK),which links LPPE1 and KE,is determined by the vertical velocity and atmospheric stability.Corresponding to warm air ascending or cold air descending,the conversion term is positive,indicating that LPPE1 transforms to KE,and vice verse.At 850 hPa,the conversion term is featured by the maxima over the Intertropical Convergence Zone and most monsoon regions,and CK is also positive over the storm track region in the Northern Hemisphere and in the westerly belt in the Southern Hemisphere.This is applied to the energy budget of SCSSM activity;the conversion term grows rapidly in the phase of SCSSM revival and subsequently dominates in the active phase of SCSSM.In the active phase of SCSSM,the conversion term is about 2-3 times as much as the energy flux transported through the boundary,indicating that the conversion term plays a crucial role in SCSSM revival and active SCSSM.In addition,the condition of active SCSSM is explored,the results show that when LPPE1 equals its summer climatological normals,SCSSM tends to be active if the ascending velocity exceeds the threshold velocity.