Refractive index and derived molecular properties of some gases determined by dispersive fourier transform spectroscopy (DFTS) in the visible wave number range

1988 ◽  
Vol 94 (1-6) ◽  
pp. 207-209 ◽  
Author(s):  
Klaus Kerl ◽  
Henry H�usler
Keyword(s):  
Refractive Index ◽  
Fourier Transform ◽  
Fourier Transform Spectroscopy ◽  
Molecular Properties ◽  
Wave Number ◽  
Number Range ◽  
Wave Number Range ◽  
Dispersive Fourier Transform Spectroscopy

Dispersive Fourier Transform Spectroscopy Of Free-Standing Porous Silicon Films

1997 ◽  
Vol 486 ◽  
Author(s):  
J. Salonen ◽  
K. Saarinen ◽  
J. Peura ◽  
J. Vilnikanoja ◽  
I. Salomaa ◽  
...  
Keyword(s):  
Refractive Index ◽  
Fourier Transform ◽  
Porous Silicon ◽  
Absorption Coefficient ◽  
Optical Constants ◽  
Fourier Transform Spectroscopy ◽  
Silicon Films ◽  
Spectral Variation ◽  
Free Standing ◽  
Dispersive Fourier Transform Spectroscopy

AbstractWe have investigated optical constants of free-standing porous silicon films by dispersive Fourier transform spectroscopy (DFTS) in the NIR-VIS range. This allows the spectral variation of both the absorption coefficient and the refractive index of a material to be determined from the measurements of the attenuation and phase shift imposed on an electromagnetic wave by its interaction with a specimen. Using these optical constants, we have studied the complex dielectric function and the complex conductivity. To avoid the additive error in the absorption spectra arising from the pseudocoherence, we measured the transmission spectra by conventional Fourier transform spectroscopy (FTS). Using the refraction spectrum derived from the DFTS measurements, we have corrected for reflection losses in calculation of the absorption spectrum from the FTS transmission spectrum. The changes in the absorption coefficient and the refractive index due to oxidation, which is the most common aging phenomenon in porous silicon, have been studied using samples with different types of oxidization.

Far-infrared properties of helium-doped silicon

2015 ◽  
Vol 93 (8) ◽  
pp. 935-940
Author(s):  
Wei Ren ◽  
Qingyan Zhou ◽  
Bing Li ◽  
Hongxiang Deng ◽  
Shaobo Han ◽  
...  
Keyword(s):  
Refractive Index ◽  
Absorption Coefficient ◽  
Single Crystal Silicon ◽  
Far Infrared ◽  
Wave Number ◽  
Crystal Silicon ◽  
Number Range ◽  
Temperature Range ◽  
Transmission Electron ◽  
Wave Number Range

Single crystal silicon is an important material used for semiconductor devices and also a potential material in device research. Far-infrared optical properties are studied for the helium ion implanted samples with different fluences of 5.0 × 1016, 1.0 × 1017, 2.0 × 1017, and 4.0 × 1017 cm−2. The absorption coefficient and refractive index of silicon with different helium concentrations are measured in the wave number range from 4 to 85 cm−1 and temperature range from 145 to 520 K. The results show that the absorption coefficient increases with increasing fluence of helium ions, but the refractive index decreases. The correlations between absorption coefficient and refractive index and temperature of all samples are similar. The refractive index increases with temperature in the whole measurement temperature range, but the absorption coefficient has different trends in the different wavebands. The absorption coefficient decreases with the increase of temperature in the region below 12 cm−1; however, the absorption coefficient increases when the wave number is larger than 30 cm−1. The absorption coefficient curves at different wavebands are well fitted by the Drude model. A large number of helium bubbles and defects, such as voids and dislocations have been observed in the implanted area by transmission electron microscopy (TEM), which contributes to the increase of optical absorption.

Universality hypothesis for the small wave-number range of decaying turbulence

1995 ◽  
Vol 45 (6) ◽  
pp. 517-520
Author(s):  
L. Ts. Adzhemyan ◽  
M. Hnatich ◽  
M. Stehlik
Keyword(s):  
Wave Number ◽  
Number Range ◽  
Wave Number Range ◽  
Small Wave ◽  
Small Wave Number ◽  
Decaying Turbulence

Inviscid instability of an unbounded heterogeneous shear layer

1971 ◽  
Vol 48 (2) ◽  
pp. 405-415 ◽  
Author(s):  
S. A. Maslowe ◽  
R. E. Kelly
Keyword(s):  
Growth Rate ◽  
Froude Number ◽  
Mixing Layer ◽  
Density Variation ◽  
Wave Number ◽  
Unstable Wave ◽  
Number Range ◽  
Spatial Growth ◽  
Wave Number Range ◽  
Low Froude Number

Stability curves are computed for both spatially and temporally growing disturbances in a stratified mixing layer between two uniform streams. The low Froude number limit, in which the effects of buoyancy predominate, and the high Froude number limit, in which the effects of density variation are manifested by the inertial terms of the vorticity equation, are considered as limiting cases. For the buoyant case, although the spatial growth rates can be predicted reasonably well by suitable use of the results for temporal growth, spatially growing disturbances appear to have high group velocities near the lower cutoff wave-number. For the inertial case, it is demonstrated that density variations can be destabilizing. More precisely, when the stream with the higher velocity has the lower density, both the wave-number range of unstable disturbances and the maximum spatial growth rate are increased relative to the case of homogeneous flow. Finally, it is shown how the growth rate of the most unstable wave in the inertial case diminishes as buoyancy becomes important.

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