Angle-dependent study of a direct optical transition in thespbands of Ag(111) by one- and two-photon photoemission

2007 ◽  
Vol 76 (19) ◽  
Author(s):  
Aimo Winkelmann ◽  
Vahit Sametoglu ◽  
Jin Zhao ◽  
Atsushi Kubo ◽  
Hrvoje Petek
Keyword(s):  
Optical Transition ◽  
Two Photon ◽  
Direct Optical Transition

scholarly journals Progresses on the Use of Two-Photon Absorption Laser Induced Fluorescence (TALIF) Diagnostics for Measuring Absolute Atomic Densities in Plasmas and Flames

Plasma ◽  
2021 ◽  
Vol 4 (1) ◽  
pp. 145-171
Author(s):  
Kristaq Gazeli ◽  
Guillaume Lombardi ◽  
Xavier Aubert ◽  
Corinne Y. Duluard ◽  
Swaminathan Prasanna ◽  
...  
Keyword(s):  
Optical Transition ◽  
Thin Film Deposition ◽  
Laser Induced Fluorescence ◽  
Film Deposition ◽  
Stimulated Emission ◽  
Photon Absorption ◽  
Collisional Quenching ◽  
Two Photon Absorption ◽  
Two Photon ◽  
Wide Range

Recent developments in plasma science and technology have opened new areas of research both for fundamental purposes (e.g., description of key physical phenomena involved in laboratory plasmas) and novel applications (material synthesis, microelectronics, thin film deposition, biomedicine, environment, flow control, to name a few). With the increasing availability of advanced optical diagnostics (fast framing imaging, gas flow visualization, emission/absorption spectroscopy, etc.), a better understanding of the physicochemical processes taking place in different electrical discharges has been achieved. In this direction, the implementation of fast (ns) and ultrafast (ps and fs) lasers has been essential for the precise determination of the electron density and temperature, the axial and radial gradients of electric fields, the gas temperature, and the absolute density of ground-state reactive atoms and molecules in non-equilibrium plasmas. For those species, the use of laser-based spectroscopy has led to their in situ quantification with high temporal and spatial resolution, with excellent sensitivity. The present review is dedicated to the advances of two-photon absorption laser induced fluorescence (TALIF) techniques for the measurement of reactive species densities (particularly atoms such as N, H and O) in a wide range of pressures in plasmas and flames. The requirements for the appropriate implementation of TALIF techniques as well as their fundamental principles are presented based on representative published works. The limitations on the density determination imposed by different factors are also discussed. These may refer to the increasing pressure of the probed medium (leading to a significant collisional quenching of excited states), and other issues originating in the high instantaneous power density of the lasers used (such as photodissociation, amplified stimulated emission, and photoionization, resulting to the saturation of the optical transition of interest).

Selective 4H-SiC UV Detectors

2013 ◽  
Vol 740-742 ◽  
pp. 1014-1017
Author(s):  
Evgenia V. Kalinina ◽  
O. Konstantinov ◽  
A.A. Lebedev ◽  
Yu. Gol’dberg
Keyword(s):  
Quantum Efficiency ◽  
Uv Radiation ◽  
Wavelength Range ◽  
Optical Transition ◽  
Human Beings ◽  
Radiation Level ◽  
Uv Detectors ◽  
Uv Photodetectors ◽  
Oncological Diseases ◽  
Direct Optical Transition

Carcinogenic (bactericidal) radiation (λ = 200–300 nm with a peak at 254 nm) is present in natural (Sun) and artificial (lamps) source of UV radiation. Its intensity is very low as compared to other types of radiation, but it strongly affects the health of human beings. To prevent oncological diseases, it is important to monitor the carcinogenic radiation level; i.e., selective photodetectors are required. A UV photodetectors based on n-4H-SiC Schottly barriers and p+-n junctions are proposed. The quantum efficiency spectrum of such detectors is very close to the spectrum of relative action of carcinogenic radiation on human beings due to the direct optical transition at 4.9 eV in 4H-SiC. The quantum efficiency (at the spectral peak 254 nm) amounts to about 0.3 electrons/photon for virtually zero sensitivity in other spectral regions. Quantum efficiency in the wavelength range 247–254 nm is practically independent of temperature in the range from −100 to +300°C.

Optical Properties and New Functionality of Nanocrystalline CuCl and Ge

1992 ◽  
Vol 283 ◽  
Author(s):  
Yasuaki Masumoto
Keyword(s):  
Optical Transition ◽  
Optical Gain ◽  
Glassy Matrix ◽  
Bulk Crystals ◽  
Electron Microscopic ◽  
Visible Photoluminescence ◽  
Resolution Electron ◽  
Microscopic Studies ◽  
Direct Optical Transition ◽  
First Time

ABSTRACTLasing of nanocrystalline CuCl embedded in a NaCl single crystal wasobserved for the first time. Lasing takes place at 77 K in nanocrystalline CuCl sandwiched between dielectric mirrors under the pulsed ultraviolet laser excitation. The lasing transition is that from bi-exciton to exciton. The lasing is observed up to 108 K. The optical gain of nanocrystalline CuCl is almost the same as that of bulk crystals in spite of the low concentration of CuCl in the NaCl matrix.The origin of visible photoluminescence of nanocrystalline Ge in SiO2 glassy matrix has been studied. Spectroscopic analyses of nanocrystalline Ge indicate that the room-temperature photoluminescence comes from nanocrystalline Ge of diameter of 4 nm or less. High-resolution electron microscopic studies imply that the structure of nanocrystalline Ge of diameter ≤ 4 nm differs from the diamond structure. These data suggest that new nanostructure crystalline Ge having a character of direct optical transition exhibits the visible photoluminescence.

Sulphur-selenium compounds

1969 ◽  
Vol 22 (11) ◽  
pp. 2301 ◽  
Author(s):  
CR Ailwood ◽  
PE Fielding
Keyword(s):  
Optical Absorption ◽  
Absorption Edge ◽  
Mass Spectra ◽  
Optical Transition ◽  
Optical Absorption Edge ◽  
X Ray Diffraction ◽  
Selenium Compounds ◽  
X Ray ◽  
Direct Optical Transition

The characterization of various mixtures obtained by fractional recrystallization of sulphur-selenium melts is described. Optical absorption spectra of thin films, mass spectra, and X-ray diffraction data reveal two distinct ranges of homogeneity, the break occurring at 14 at. % Se. The optical absorption edge of crystals containing less than 14 at. % Se varies linearly with composition. A direct optical transition to the conduction band of S8 and a transition due to trapped excitons are thought to contribute to the excessive width of this absorption edge.

ENERGY-GAP VARIATION IN MIXED III–V ALLOYS

1967 ◽  
Vol 45 (2) ◽  
pp. 255-261 ◽  
Author(s):  
A. G. Thompson ◽  
J. C. Woolley
Keyword(s):  
Optical Absorption ◽  
Mole Fraction ◽  
Energy Gap ◽  
Optical Transition ◽  
Empirical Relation ◽  
Energy Gaps ◽  
Direct Optical Transition ◽  
Crystal Type ◽  
The Mean ◽  
Alloy Systems

Values of E0, the lowest direct optical transition, are available for several III-V alloy systems, from measurements of optical absorption, electroreflectance, electroluminescence, etc. It is shown that in all available cases the variation of E0 with composition can be fitted very well to an equation of the form E0 = A + Bx + Cx2, where x is the mole fraction of one component compound. Such a relation is expected from a virtual-crystal type of analysis.If E0m is the mean of the energy gaps of the component compounds of the system, it is found that an empirical relation of the form [Formula: see text] appears to hold where α is approximately 0.3 eV3/2.

Appearance of Quasi-Direct Optical Transition from Si Network in SiO2-Doped Si Films

1993 ◽  
Vol 32 (Part 2, No. 8B) ◽  
pp. L1148-L1149
Author(s):  
Yukio Osaka ◽  
Fumitaka Toyomura ◽  
Hideyuki Katayama ◽  
Kenji Kohno
Keyword(s):  
Optical Transition ◽  
Direct Optical Transition ◽  
Si Films
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