Search results for "photoelectric effect"
showing 10 items of 57 documents
Electron spin polarization in the photoemission of NEA GaAs1?x P x
1982
Negative electron affinity GaAs1−xPx-photocathodes emit spin-polarized electrons if irradiated with circularly polarized light. The spectra of spin polarization of photoelectrons emitted from crystals with different phosphorus contentx resemble each other in shape but shift to shorter wavelengths with increasingx. Polarization values up to 40% are observed for electrons from crystals withx=0 andx=0.38. Cathodes with higher phosphorus contents increasing fromx=0.65 tox=0.87 and tox = 1.0 deliver photoelectrons with decreasing degrees of spin polarization of 17%, 15%, and 9%, respectively, at maximum.
Photoelectron-holography using circularly polarized light
1999
Abstract Circular dichroism in the angular distribution of photoelectrons (CDAD) is not only observed from aligned initial states, but also as a consequence of the scattering of photoelectrons at the surrounding atoms in a solid or an adsorbate. Using the analytical result for the CDAD, we show that it is an integral transformation of the product of the angular momentum of the emitted electron and the Fourier-transformed scattering potential of the surrounding atoms. Therefore, we interpret the CDAD pattern as photoelectron-hologram. The real space distribution of atoms can be reconstructed by an inverse integral transformation of the CDAD pattern, which carries the full phase-information. …
Circular dichroism in x-ray photoemission from core levels of nonmagnetic species
1992
Circular dichroism in the angular distribution of photoelectrons (CDAD) has been observed in core-level photoemission from spherically symmetric initial states of nonmagnetic species utilizing circularly polarized soft-x-ray radiation from BESSY. Up to now, CDAD was predicted and observed only for aligned initial states. The data for oriented CO molecules prove that circular x-ray dichroism in photoemission from core levels is a general phenomenon that is not restricted to ferromagnets. High asymmetries of 50% suggest future applications as an effective circular x-ray analyzer.
Linear Dichroism in Photoemission from Oriented Molecules
1993
It is shown that oriented molecules reveal both Linear Dichroism (LD) and Linear Dichroism in the Angular Distribution (LDAD) of photoelectrons, which means a difference between photoelectron currents ejected at a definite angle by linearly polarized light of two mutually perpendicular polarizations. Measurements of LD and LDAD enable one to investigate the orientation of molecules and to make an essential step towards the complete quantummechanical experiment. As an example, LDAD in a model case of oriented heteronuclear diatomic molecules is presented.
Untersuchung verschiedener Elektronenemissionsprozesse auf Mehrfachemission
1965
A comparison of the pulse hight distribution of several electron emission processes is drawn. Thermionic electrons, photoelectrons, field electrons and exoelectrons are found to be emitted as single electrons.
Low noise scintillation detectors with a P-47 thin layer screen for electrons of several keV
1994
Abstract The applicability of a low-noise scintillation detector (ScD) for the registration of electrons of several keV energy has been studied employing photomultipliers (PM) of different types and sizes. With the application of a sedimented P-47 scintillation screen, the values of the low-energy sensitivity limit and those of the light conversion coefficient were determined as about 2.7–4.7 keV and 2.8–6.6 photoelectrons/keV, respectively, for the set of PM's (Philips-Valvo XP 2020, Philips-Valvo XP 2052, Philips-Valvo XP 2972, EMI 9124a) studied. It is concluded that such scintillation detectors might be used advantageously as electron counters in the range of E > 5 keV. Applications bel…
Electron-TOF-analyser for complete momentum analysis in photoemission from surfaces
2001
Abstract We present a new method for momentum-selective imaging by means of a time-of-flight (TOF) technique. The instrument employs a time- and space-resolving delayline detector in combination with a parabolic electrostatic field and a drift space. We use this kind of spectrometer, to raise the efficiency of experiments, which are total momentum resolved. The main difference to conventional photoemission experiments using a rotatable spectrometer is the simultaneous detection of all emitted photoelectrons. In addition to this feature, the angular distribution should be directly visible, to observe solid state symmetries. In order to facilitate these requirements, we use a delayline detect…
Single-component plasma of photoelectrons
2007
Abstract Ten-nanosecond pulses of photoelectrons liberated by intense UV laser pulses from a thin gold layer are captured into a single-component plasma that is ideally suited to cool antiprotons ( p ¯ ) for antihydrogen ( H ¯ ) production. Up to a billion electrons are accumulated using a series of laser pulses, more than are needed for efficient p ¯ cooling in the large traps now being used for loading p ¯ for H ¯ production. The method is demonstrated within an enclosed vacuum space that is entirely at 4 K, and is thus compatible with the exceptional cryogenic vacuum that is desirable for the long-term storage of antihydrogen. The pitfalls of other electron accumulation methods are entir…
Photoelectric effect from a metal surface: a revisited theoretical model
1992
The Sommerfeld model extended to include radiation–electron interaction in the regime of highly intense fields is taken as the basis for studying theoretically the laser multiphoton photoelectric effect from a metal surface. Numerical analysis is carried out without approximations other than those inherent in the model itself; the study of the multiphoton aspect of the problem is based on a scheme that is nonperturbative in an essential way. The numerical analysis facilitates insight into the potential and the limits of the model in the interpretation of recent experiments and into the similarities and differences between the metal multiphoton effect and atomic multiphoton ionization. The r…
Spatially resolved observation of dynamics in electrical and magnetic field distributions by means of a delayline detector and PEEM
2005
Abstract Photoemission electron microscopy (PEEM) was exploited to observe the dynamics in local field distributions on microstrip-line devices with a best time resolution of 133 ps. A delayline detector system served as imaging unit capable of a time resolving data acquisition and processing. The setup can be operated at the resolution limit of the PEEM of about 20 nm while a continuously illuminating UV-lamp excites the photoelectrons in threshold photoemission. A pulsed photon source is not needed to obtain time resolved images, the time reference of the data acquisition was taken by a periodic signal (clock, here typ. 100 MHz) in phase with the pulse pattern applied to the microstrip-li…