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.

Electronic structure of heavily electron-doped BaFe1.7Co0.3As2 studied by angle-resolved photoemission

Abstract: We have performed high-resolution angle-resolved photoemission spectroscopy on heavily electron-doped non-superconducting (SC) BaFe1.7Co0.3As2. We find that the two hole Fermi surface pockets at the Brillouin zone center observed in the hole-doped superconducting Ba0.6K0.4Fe2As2 are absent or very small in this compound, while the two electron pockets at the zone corner significantly expand due to electron doping by the Co substitution. Comparison of the Fermi surface between non-SC and SC samples indicates that the coexistence of hole and electron pockets connected via the antiferromagnetic wave vector is essential in realizing the mechanism of superconductivity in the iron-based superconductors.

Morphological and electronic properties of ultrathin crystalline silica epilayers on a Mo(112) substrate

Abstract: Ultrathin crystalline silica layers grown on a Mo(112) substrate have been shown to be a useful silica model oxide support in surface science model catalyst studies. As the oxide support material plays an important role in the catalytic process, a multitechnique surface science study is presented to characterize the morphological and electronic properties of the heteroepitaxial system ${\mathrm{SiO}}_{2}/\mathrm{Mo}(112).$ The long-range order of the silica epilayer which grows commensurate with a $c(2\ifmmode\times\else\texttimes\fi{}2)$ surface unit mesh on the Mo(112) substrate is studied by low-energy electron diffraction (LEED). The defect structure of the silica epilayer is characterized in a spot profile analysis (SPA)-LEED study. Antiphase domain boundaries split the silica epilayer into an array of silica crystal grains whose average size and shape is determined. Aiming to prepare flat silica surfaces, the change in the surface roughness with progress in the film preparation is monitored in a combined SPA-LEED and scanning tunneling microscopy (STM) study and seen to influence also the Si-O stretching frequency in the infrared-reflection-absorption spectroscopy spectra. In STM images of the final silica film an average surface roughness of about 1 \AA{} is detected. It is possible to visualize the silica film unit cell periodicity. A combined anger electron spectroscopy and ultraviolet photoelectron spectroscopy valence band study confirms the silica film stoichiometry and the growth of a 4:2 coordinated silica polymorph on the Mo(112) surface. These various surface science studies allow us to propose models for the growth and structure of the silica epilayer on the Mo(112) surface.

Time- and angle-resolved photoemission spectroscopy of solids in the extreme ultraviolet at 500 kHz repetition rate

Abstract: Time- and angle-resolved photoemission spectroscopy (trARPES) employing a 500 kHz extreme-ultraviolet light source operating at 21.7 eV probe photon energy is reported. Based on a high-power ytterbium laser, optical parametric chirped pulse amplification, and ultraviolet-driven high-harmonic generation, the light source produces an isolated high-harmonic with 110 meV bandwidth and a flux of more than 1011 photons/s on the sample. Combined with a state-of-the-art ARPES chamber, this table-top experiment allows high-repetition rate pump-probe experiments of electron dynamics in occupied and normally unoccupied (excited) states in the entire Brillouin zone and with a temporal system response function below 40 fs.

Ab-initio angle and energy resolved photoelectron spectroscopy with time-dependent density-functional theory

Abstract: We present a time-dependent density-functional method able to describe the photoelectron spectrum of atoms and molecules when excited by laser pulses. This computationally feasible scheme is based on a geometrical partitioning that efficiently gives access to photoelectron spectroscopy in time-dependent density-functional calculations. By using a geometrical approach, we provide a simple description of momentum-resolved photoemission including multiphoton effects. The approach is validated by comparison with results in the literature and exact calculations. Furthermore, we present numerical photoelectron angular distributions for randomly oriented nitrogen molecules in a short near-infrared intense laser pulse and helium-(I) angular spectra for aligned carbon monoxide and benzene.

Electronic Structures and Chemical Bonding of Fluorinated Fullerenes Studied by NEXAFS, UPS, and Vacuum-UV Absorption Spectroscopies

Abstract: The chemical bonding and the electronic structures of C60Fx and C70Fx were investigated by near edge X-ray absorption fine structure (NEXAFS) spectroscopy and UV photoemission spectroscopy (UPS), which are useful methods for examining the unoccupied and the occupied states, respectively. With these results and XPS measurements, we derived the electronic energy diagram of C60Fx and discussed the change of the electronic structure from that of C60 by fluorination. The energies of the LUMO and the Fermi level of solid C60F48 were estimated to be −5.0 and −5.4 eV below the vacuum level, indicating that highly doped C60Fx is a strong electron acceptor. The electronic absorption spectra of C60Fx solutions deep into the vacuum-ultraviolet region were also measured, and the isomerism of C60Fx was discussed by comparing the observed results with theoretical simulations.