Conversion of UV and Visible Photons to Photoelectrons

2016 ◽  
pp. 1-8
Keyword(s):  
Work Function ◽  
Photoelectric Effect ◽  
Basic Knowledge ◽  
Great Success ◽  
Adsorbed Layers ◽  
Uv Photons

The operation of most of gaseous photomultipliers is based either on gas photoionization or on photoelectric effect from solid photocathodes. There have also been attempts to use liquid photocathodes which offer lower ionization thresholds compared to the corresponding vapors. A great success has been achieved with solid photocathodes covered with adsorbed layers of some photosensitive vapors which reduce the cathode work function and as a result extend the photosensitivity threshold towards long wavelengths. It also enhances their quantum efficiencies sometime on a factor of two. The main physic mechanisms of interactions of UV photons with gases as well as with liquid and solid photocathodes are described in detail in this chapter. This basic knowledge is important when designing and using gaseous photodetectors.

Acetylene chemisorption at palladium: Effect of temperature and structure of the surface

1984 ◽  
Vol 49 (6) ◽  
pp. 1448-1458
Author(s):  
Josef Kopešťanský
Keyword(s):  
Work Function ◽  
Atomic Hydrogen ◽  
Effect Of Temperature ◽  
Thermally Stable ◽  
Template Effect ◽  
Temperature Range ◽  
Adsorbed Layers ◽  
Different Types ◽  
Adsorption Complexes ◽  
Low Coverage

The effect of temperature and structure of the palladium surfaces on acetylene chemisorption was studied along with the interaction of the adsorbed layers with molecular and atomic hydrogen. The work function changes were measured and combined with the volumetric measurements and analysis of the products. At temperature below 100 °C, acetylene is adsorbed almost without dissociation and forms at least two different types of thermally stable adsorption complexes. Acetylene adsorbed at 200 °C is partly decomposed, especially in the low coverage region. Besides the above mentioned effects, the template effect of adsorbed acetylene was studied in the temperature range from -80° to 25 °C. It has been shown that this effect is a typical phenomenon of the palladium-acetylene system which is not due to surface impurities.

scholarly journals THE THERMAL FORM OF THE PHOTOEFFECT WITH THE DEBYE AND THE WIGNER CRYSTAL

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Miroslav Pardy ◽  
Keyword(s):  
Specific Heat ◽  
Work Function ◽  
Radiative Correction ◽  
Photoelectric Effect ◽  
Wigner Crystal ◽  
Photon Propagator ◽  
Crystal Medium

We define the photoelectric effect with the specific heat term replacing the work function. The photon propagator involving the radiative correction is also considered. We consider the Debye specific head for the 3D crystal medium, the specific heat for the 2D medium and specific heat for the Wigner crystal.

The free electron theory of metals

2018 ◽  
Author(s):  
L. Solymar ◽  
D. Walsh ◽  
R. R. A. Syms
Keyword(s):  
Distribution Function ◽  
Specific Heat ◽  
Work Function ◽  
Field Emission ◽  
Density Of States ◽  
Free Electron ◽  
Thermionic Emission ◽  
Photoelectric Effect ◽  
Electron Theory ◽  
Dirac Distribution

The model of the free electron theory is presented. The density of states and the Fermi–Dirac distribution function are discussed, leading to the specific heat of the electrons, the work function, thermionic emission, and the Schottky effects. As examples of applications the field-emission microscope and quartz–halogen lamps are discussed. The photoelectric effect and the energy diagrams relating to the junction between two metals are also discussed.

A century of Antarctic science; planning and serendipity

2005 ◽  
Vol 32 (2) ◽  
pp. 129-143 ◽  
Author(s):  
G. E. Fogg
Keyword(s):  
Modern Technology ◽  
Basic Knowledge ◽  
Great Success ◽  
Dry Valleys ◽  
Microbial Life ◽  
International Geophysical Year ◽  
Antarctic Research ◽  
Understanding Of Science ◽  
The Antarctic ◽  
Massive Accumulation

The British National Antarctic Expedition planned with discreditable bickering, sailed for the Antarctic in 1901 on the Discovery. The venture was well equipped and commanded by R. F. Scott who, without scientific training himself, was nevertheless remarkably in empathy with his scientists. The expedition was foremost among those dispatched around the same time in establishing basic knowledge of the continent. Followed by the second Scott expedition and those of Shackleton and Mawson, a cadre of able and enthusiastic scientists was established. The second involvement of the Discovery in Antarctic exploration was planned without quarrels and with unusual understanding of science by a government department, resulting in a massive accumulation of knowledge about the Southern Ocean. United States expeditions began in 1928, introducing modern technology, thereby extending greatly the scope of Antarctic research. The Norwegian-British-Swedish expedition of 1949–1952 put planned science before geographical exploration. The International Geophysical Year of 1957–1958, supported by governments and planned by international committees, achieved great success. Science has flourished in Antarctica with unplanned and serendipitous findings emerging, for example, the structure of the magnetosphere, collection of meteorites by ice movements, the microbial life of the apparently sterile Dry Valleys and the discovery of the ozone “hole”.

A Novel Method for True Work Function Determination of Metal Surfaces by Combined Kelvin Probe and Photoelectric Effect Measurements

2000 ◽  
Vol 619 ◽  
Author(s):  
Bert Lägel ◽  
Iain D. Baikie ◽  
Konrad Dirscherl ◽  
Uwe Petermann
Keyword(s):  
Thin Film ◽  
Work Function ◽  
Metal Surfaces ◽  
Surface Condition ◽  
High Vacuum ◽  
Photoelectric Effect ◽  
Ultra High Vacuum ◽  
Kelvin Probe ◽  
Novel Method

ABSTRACTWe have developed a novel method for in-situ measurements of the true work function (ø) of metal surfaces by combined ultra-high vacuum compatible Kelvin Probe and photoelectric effect measurements. The work function is an extremely sensitive parameter of surface condition and can be used to study oxidation and thin film growth on metal surfaces. For example, the increase in ø due to oxidation of polycrystalline rhenium is 1.9eV.The Kelvin Probe measures local work function differences between a conducting sample and a reference tip in a non-contact, truly non-invasive way over a wide temperature range. However, it is an inherently relative technique and does not provide an absolute work function if the work function of the tip (øtip) is unknown.We present a novel approach to measure øtip with the Kelvin Probe via the photoelectric effect, using a Gd foil as the photoelectron source, hereby combining the advantages of both methods to provide the absolute work function of the sample surface. We demonstrate the application of the technique by in-situ work function measurements during oxidation of polycrystalline rhenium. The extended Kelvin Probe method therefore has potential applications as a characterisation tool for thin film epitaxy and work function engineering of surfaces.

scholarly journals Advances in Deep Learning Methods for Visual Tracking: Literature Review and Fundamentals

2021 ◽  
Author(s):  
Xiao-Qin Zhang ◽  
Run-Hua Jiang ◽  
Chen-Xiang Fan ◽  
Tian-Yu Tong ◽  
Tao Wang ◽  
...  
Keyword(s):  
Deep Learning ◽  
Object Tracking ◽  
Visual Tracking ◽  
Adaptive Methods ◽  
Basic Knowledge ◽  
Visual Object ◽  
Model Parameters ◽  
Great Success ◽  
Single Object ◽  
Learning Methods

AbstractRecently, deep learning has achieved great success in visual tracking tasks, particularly in single-object tracking. This paper provides a comprehensive review of state-of-the-art single-object tracking algorithms based on deep learning. First, we introduce basic knowledge of deep visual tracking, including fundamental concepts, existing algorithms, and previous reviews. Second, we briefly review existing deep learning methods by categorizing them into data-invariant and data-adaptive methods based on whether they can dynamically change their model parameters or architectures. Then, we conclude with the general components of deep trackers. In this way, we systematically analyze the novelties of several recently proposed deep trackers. Thereafter, popular datasets such as Object Tracking Benchmark (OTB) and Visual Object Tracking (VOT) are discussed, along with the performances of several deep trackers. Finally, based on observations and experimental results, we discuss three different characteristics of deep trackers, i.e., the relationships between their general components, exploration of more effective tracking frameworks, and interpretability of their motion estimation components.

A Novel Approach for True Work Function Determination of Electron-Emissive Materials by Combined Kelvin Probe and Photoelectric Effect Measurements

2000 ◽  
Vol 621 ◽  
Author(s):  
Bert Lägel ◽  
Iain D. Baikie ◽  
Konrad Dirscherl ◽  
Uwe Petermann
Keyword(s):  
Work Function ◽  
High Vacuum ◽  
Sample Surface ◽  
Photoelectric Effect ◽  
Ultra High Vacuum ◽  
Chemical Contamination ◽  
Kelvin Probe ◽  
Non Invasive ◽  
Novel Approach ◽  
The Stability

ABSTRACTFor the development of new electron-emissive materials knowledge of the work function Φ and changes in Φ is of particular interest. Among the various methods, the ultra-high vacuum (UHV) compatible scanning Kelvin Probe has been proven to be a superior technique to measure work function changes due to e.g. UHV cleaning processes, chemical contamination, thermal processing etc. with high accuracy (<1meV).The Kelvin Probe measures local work function differences between a conducting sample and a reference tip in a non-contact, truly non-invasive way over a wide temperature range. However, it is an inherently relative technique and does not provide an absolute work function if the work function of the tip (Φtip) is unknown.Here, we present a novel approach to measure Φtip with the Kelvin Probe via the photoelectric effect, where a Gd foil is used as the photoelectron source. This method thus provides the true work function of the sample surface with an accuracy of approx. 50meV. We demonstrate the application of the technique by in situ work function measurements on evaporated layers of the low work function material LaB6 on a Re substrate and follow the changes in Φ of LaB6 due to the surface adsorption of residual gas molecules. Thus, the extended Kelvin Probe method provides an excellent tool to characterise and monitor the stability of low work function surfaces.

Functional information from magnetic resonance imaging

1995 ◽  
Vol 53 ◽  
pp. 84-85
Author(s):  
Alan P. Koretsky ◽  
Afonso Costa e Silva ◽  
Yi-Jen Lin
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
High Resolution ◽  
Cancer Biology ◽  
Imaging Modality ◽  
Magnetic Resonance Images ◽  
Great Success ◽  
Functional Information ◽  
Resonance Imaging ◽  
High Resolution Mri

Magnetic resonance imaging (MRI) has become established as an important imaging modality for the clinical management of disease. This is primarily due to the great tissue contrast inherent in magnetic resonance images of normal and diseased organs. Due to the wide availability of high field magnets and the ability to generate large and rapidly switched magnetic field gradients there is growing interest in applying high resolution MRI to obtain microscopic information. This symposium on MRI microscopy highlights new developments that are leading to increased resolution. The application of high resolution MRI to significant problems in developmental biology and cancer biology will illustrate the potential of these techniques.In combination with a growing interest in obtaining high resolution MRI there is also a growing interest in obtaining functional information from MRI. The great success of MRI in clinical applications is due to the inherent contrast obtained from different tissues leading to anatomical information.

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