Photoemission spectroscopy

About: Photoemission spectroscopy is a research topic. Over the lifetime, 10821 publications have been published within this topic receiving 250888 citations. The topic is also known as: photoelectron spectroscopy & PES.

Charge redistribution and electronic behavior in a series of Au-Cu alloys.

Abstract: A series of Au-Cu alloys of various stoichiometries and order have been studied using x-ray photoemission spectroscopy (XPS) and x-ray absorption spectroscopy (XAS) Significant electronic changes are associated with alloying and with changes in the local environment The Au 5d electron charge depletion has been determined independently from XPS core-level and M\"ossbauer isomer shifts and from x-ray absorption near-edge structure (XANES) measurements Strong correlations were found using both methods in the parameters investigated here, especially in the elucidation of the charge-transfer mechanism It is found that at the Au site there is a loss of d charge, upon alloying, which increases as Au becomes more dilute in Cu This along with XANES evidence of d charge gain at the Cu site, conduction (primarily 6s) charge gain at the Au site, and overall charge gain at the Au site verifies the charge compensation model in which Au loses d charge but is overcompensated by a gain of conduction charge This observation is in line with electronegativity (Au is more electronegative than Cu) and electroneutrality (the overall gain of charge is small) arguments It is also found that there is a strong linear correlation between the 5d hole count at the Au site and (1) the M\"ossbauer isomer shift, (2) alloy d-band width, (3) ``Au'' apparent spin-orbit splitting in the alloy d band By comparing the ordered and disordered species (which have different local environments) it is found that the charge transfer depends primarily on the local environment (coordination number of like and unlike atoms) and not on atomic separation The charge transfer (d-band depletion) was larger in the ordered species and can be explained by the number of Cu and Au nearest neighbors as compared to the disordered phases

Spectroscopy of image-potential states with inverse photoemission.

Abstract: Cu(100), Cu(110), Ag(111},Au(111), and Au(100}), a semimetal [Sb(100}],and a layered compound {1T-TiS2). Data for Au{111) show that image-potential states exist even in the presence of bulk states. The coupling with bulk states is weak as indicated by the narrow {&0.1 eV) width of the image states. The binding energies of the lowest state cluster around 0.7 eV for a variety of metal and semimetal surfaces indicating a universal phenomenon. This value is close to the hydrogenic binding energy of —, 6 Ry -0.85 eV for the n =1 state, which indicates that the simple Coulombic image potential dominates the energy balance.

Hot-electron dynamics at Cu(100), Cu(110), and Cu(111) surfaces:mComparison of experiment with Fermi-liquid theory

Abstract: Lifetimes of hot electrons in the 1.3--3.2-eV energy range at low index surfaces of Cu((100),(110),(111)) are measured by two-photon time-resolved photoemission spectroscopy with 10 fs resolution. Energy dependence of the lifetimes deviates from the (E-${\mathrm{E}}_{\mathrm{F}}$${)}^{\mathrm{\ensuremath{-}}2}$ functional form predicted by the standard Fermi-liquid theory for free-electron metals, but a qualitative agreement with the theory is obtained by calculating the e-e scattering times from the band structure of Cu. However, the magnitude of the calculated lifetimes, assuming Thomas-Fermi screening length, is still about six times smaller than the measured. The failure of the free-electron model in predicting the energy dependence and magnitude of the scattering times is attributed in part to d-band electrons, which have a maximum density at -2 eV and can participate both in scattering and screening of hot electrons. The measured lifetimes also show a modest dependence on the crystal face, which is not reproduced by the band-structure calculations. The origins of this anisotropy may include coherence effects in the excitation, anisotropies in the e-e scattering cross sections, a contribution from e-p scattering to the hot-electron decay, or differences in surface electronic structure.

A photoelectron spectroscopy and ab initio study of B21-: negatively charged boron clusters continue to be planar at 21.

Abstract: The structures and chemical bonding of the B21− cluster have been investigated by a combined photoelectron spectroscopy and ab initio study The photoelectron spectrum at 193 nm revealed a very high adiabatic electron binding energy of 438 eV for B21− and a congested spectral pattern Extensive global minimum searches were conducted using two different methods, followed by high-level calculations of the low-lying isomers The global minimum of B21− was found to be a quasiplanar structure with the next low-lying planar isomer only 19 kcal/mol higher in energy at the CCSD(T)/6-311-G* level of theory The calculated vertical detachment energies for the two isomers were found to be in good agreement with the experimental spectrum, suggesting that they were both present experimentally and contributed to the observed spectrum Chemical bonding analyses showed that both isomers consist of a 14-atom periphery, which is bonded by classical two-center two-electron bonds, and seven interior atoms in the planar str