Search results for "photoelectric effect"
showing 10 items of 57 documents
Dielectric properties of potassium–sodium niobate ceramics at low frequencies
2016
ABSTRACTA study of the effects of ageing history on the electrical properties of lead-free ferroelectric ceramics of (K0.5Na0.5)(Nb1−xSbx)O3 + 0.5 mol% MnO2 and (K0.5Na0.5)(Nb1−xTax)O3 + 0.5 mol%MnO2 for x = 0.05 is reported. The samples after storage at a constant temperature have been subject to infra-low-frequency electric field and radiation. Differences of the photoelectric response between the two examined compounds were found and the restoration of polarisation in the aged ceramic materials by cycles of applied field is discussed.
Suppression of the vacuum space-charge effect in fs-photoemission by a retarding electrostatic front lens
2021
Review of scientific instruments 92(5), 053703 (2021). doi:10.1063/5.0046567
A graphene-based neutral particle detector
2019
A neutral particle detector is presented, in which the traditionally used target material, indium tin oxide (ITO), is replaced by graphene. The graphene-based detector enables collinear photodetachment measurements at a significantly shorter wavelength of light down to 230 nm compared to ITO-based detectors, which are limited at 335 nm. Moreover, the background signal from the photoelectric effect is drastically reduced when using graphene. The graphene based detector, reaching 1.7 eV further into the UV energy range, allows increased possibilities for photodetachment studies of negatively charged atoms, molecules, and clusters.A neutral particle detector is presented, in which the traditio…
Microscopic Revelation of Charge-Trapping Sites in Polymeric Carbon Nitrides for Enhanced Photocatalytic Activity by Correlating with Chemical and El…
2019
The influences of chemical and electronic structures on the photophysical properties of polymeric carbon nitrides (PCNs) photocatalysts, which govern the microscopic mechanisms of the superior photocatalytic activity under visible-light irradiation, have been resolved in this work. Time-resolved photoluminescence and in situ electron paramagnetic resonance measurements indicate that the photoexcited electrons in the fractured PCNs swiftly transfer to the C2p-localized states where the trapped photoelectrons exhibit longer lifetime compared to those in the ordinary PCNs. Moreover, the structure deviation at the carbon (Cb) atoms around the bridging sites of heptazine ring units, where trappe…
Nano photoelectron ioniser chip using LaB6 for ambient pressure trace gas detection
2012
A detector including a nanoscaled ioniser chip that surmounts the limitation of conventional photo ionisation detectors is presented. Here, ionisable gaseous substances can be detected by photoelectrons accelerated to the ionisation potential of the incoming gaseous molecules. Thin lanthanum hexaboride (LaB"6) films deposited by pulsed laser technique (PLD) serve as the air stable photocathode material representing the basis of the ioniser chip of the detector. Besides the analysis of the emission behaviour of the photocathode in vacuum and at atmospheric pressure, the detection of different volatile alcohols using the detector with a low-energy UV LED instead of a PID (VUV photon source) w…
A semiempirical correlation between the optical band gap of hydroxides and the electronegativity of their constituents
2000
In analogy with previous results on anhydrous oxides, a correlation is proposed between the optical band gap of hydroxides and the electronegativities of their constituents. Based on the experimental results on passive hydrated layers on metals obtained in our laboratory and the literature data, it is found that the hydroxide band gap varies with the square of the difference between the electronegativities of the metallic cation and the hydroxyl group. Like in the case of anhydrous oxides, two different interpolation lines have been found forsp-metal andd-metal hydroxides, respectively. The proposed correlations predict semiconducting or insulating behavior even for the most electronegative…
Fe 2p photoemission magnetic dichroism with linearly polarized synchrotron radiation and with unpolarized A1 Kα radiation
1997
We report on the measurements and analysis of Fe 2p magnetic dichroism in the angular distribution of the photoelectrons from remanently magnetized Fe(100)surfaces with unpolarized, monochromatized A1 Kα X-rays of 1486 eV energy (MDAD)and with linearly polarized synchrotron radiation of energy 800 eV (LMDAD). The two experiments verify the atomic photoionization model of (L)MDAD including the dichroism effect between field-averaged experiments of different chirality.
Influence of the symmetry on the circular dichroism in angular resolved core-level photoemission
2002
The model for angular resolved photoemission from adsorbed atoms is extended to account for the non-axial symmetry of atoms in a crystal field. In particular, circular dichroism in the angular distribution (CDAD) is theoretically investigated. A special emphasis is put on the case when incident photons are propagating along the principal axis of an atom in Cnv symmetry. The model, although mainly developed for adsorbates, may also be used as a base for emission from solid surfaces. An extension to simple bulk symmetries, like D for hexagonal or O for cubic crystals, is included. The CDAD 6 hh for normal incidence does not vanish in the extended model and reflects the symmetry of the adsorpt…
Dichroism in VUV photoemission from the (0001)-surfaces of ultrathin Gd and Nd films on W(110)
1997
Abstract Ultrathin layers of Gd and Nd epitaxially grown on W(110) have been investigated using linearly and circularly polarised light at the 6.5 m NIM beamline at the BESSY storage ring in Berlin. The high quality of the films was monitored by the sharp and dispersionless surface state just below the Fermi energy. The CDAD (circular dichroism in the angular distribution of photoelectrons) measurements showed strong effects in the surface states as well as in the valence bands. The LMDAD (linear magnetic dichroism in…) from Gd(0001) showed a small, but significant splitting of the surface state. This splitting can be reproduced by numerical one-step calculations based on spin-dependent sur…
EFFECT OF SURFACTANT AND SUBSTRATE TEMPERATURE ON THE GROWTH OF Ag FILMS ON A SAPPHIRE SURFACE
1997
The possibility of modification of the thin film growth on an insulating (sapphire) substrate by using a Ga monolayer as a "surfactant" was studied. We found that the films grown in this way are electrically conducting and can emit photoelectrons at much lower thickness than those deposited on a pure substrate. The surfactant stabilizes the positions of Ag atoms on the substrate surface and inhibits the coalescence of small nuclei into bigger islands, even when the film is annealed to 450 K. This fact may be very important for thin metal film technology.