INDUCED INFRARED ABSORPTION IN HYDROGEN AND HYDROGEN - FOREIGN GAS MIXTURES AT PRESSURES UP TO 1500 ATMOSPHERES

1954 ◽  
Vol 32 (4) ◽  
pp. 291-312 ◽  
Author(s):  
D. A. Chisholm ◽  
H. L. Welsh
Keyword(s):  
Kinetic Energy ◽  
Absorption Band ◽  
Absorption Coefficient ◽  
Infrared Absorption ◽  
High Frequency ◽  
Absorption Process ◽  
Rate Of Increase ◽  
Frequency Components ◽  
Relative Kinetic ◽  
Gas Pressures

The pressure-induced fundamental infrared absorption band of hydrogen has been investigated in the pure gas and in hydrogen–helium, hydrogen–nitrogen, and hydrogen–argon mixtures for gas pressures up to 1500 atm. and temperatures in the range 80°–376°K. At the higher densities the rate of increase of the integrated absorption coefficient with density is anomalously large; this effect is interpreted in terms of finite molecular volumes. The Q branch has been shown to consist of three components QP, Qq, and QR. The separation of the maxima in the low- and high-frequency components, QP and QR, depends on the perturbing gas and increases linearly with its density; the separation and relative intensities of the components are also strongly dependent on the temperature. It is proposed that this splitting of the Q branch is caused by the participation of the relative kinetic energy of the colliding molecules in the absorption process for collisions in the region of overlap forces. The Qq component and the S lines show no splitting and are probably produced by collisions in the region of quadrupole interaction.

THE PRESSURE-INDUCED ROTATIONAL ABSORPTION SPECTRUM OF HYDROGEN: I. A STUDY OF THE ABSORPTION INTENSITIES

1959 ◽  
Vol 37 (3) ◽  
pp. 362-376 ◽  
Author(s):  
Z. J. Kiss ◽  
H. P. Gush ◽  
H. L. Welsh
Keyword(s):  
Absorption Spectrum ◽  
Kinetic Energy ◽  
Infrared Spectrum ◽  
Absorption Coefficient ◽  
Quadrupole Interaction ◽  
Vibrational Band ◽  
Absorption Process ◽  
Relative Kinetic ◽  
Good Agreement ◽  
Gas Pressures

The pressure-induced infrared spectrum of H2 and mixtures of H2 with N2, He, Ne, A, Kr, and Xe was measured in the region 300–1400 cm−1 at total gas pressures up to 250 atm at 300° K and, where possible, at 195° K and 85° K. The spectrum shows greatly broadened S lines (ΔJ = + 2) with half widths which decrease as the temperature is lowered. The integrated absorption coefficient of the band is of the form [Formula: see text], where ρƒ is the density of the perturbing gas, except in the case of Xe for which a cubic term, [Formula: see text], is also necessary. The binary coefficient α1 increases by a factor of 28 in going from He to Xe. The theoretical band intensity, calculated on the basis of quadrupole interaction alone, is in good agreement with the experimental value only for Xe as perturbing gas; in other cases the calculated value is appreciably less than the observed value. The shape of the absorption contours suggests that the S lines are overlaid by a continuum increasing in intensity towards lower frequencies. This continuum is interpreted as the counterpart of the QR component in the vibrational band, that is, a collision-induced absorption due to overlap interaction in which the relative kinetic energy of the collision partners changes in the absorption process.

PRESSURE-INDUCED INFRARED ABSORPTION OF HYDROGEN AND HYDROGEN – FOREIGN GAS MIXTURES IN THE RANGE 1500–5000 ATMOSPHERES

1958 ◽  
Vol 36 (1) ◽  
pp. 88-103 ◽  
Author(s):  
W. F. J. Hare ◽  
H. L. Welsh
Keyword(s):  
Absorption Coefficient ◽  
Infrared Absorption ◽  
Room Temperature ◽  
Pure Hydrogen ◽  
Vibrational Transition ◽  
Absorption Process ◽  
Quadrupole Interactions ◽  
Relative Kinetic ◽  
Very High ◽  
Absorption Of Hydrogen

The pressure-induced infrared absorption of hydrogen was studied in pure hydrogen and in hydrogen–helium, hydrogen–argon, and hydrogen–nitrogen mixtures at pressures up to 5000 atm. at room temperature. The integrated absorption coefficient can be expressed in the form α1ρaρp + α2ρaρp2 over the whole range of densities (ρa = density of H2, ρp = density of the perturbing gas, [Formula: see text] in the mixture experiments). The coefficient α2 is much smaller than predicted from the effect of finite molecular volumes; this is interpreted as a partial cancellation of the induced moments in ternary collisions. The splitting of the Q branch of the fundamental, which is due to the participation of the relative kinetic energies of the colliding molecules in the absorption process, increases linearly with the density because of ternary collisions; a more rapid increase observed at very high densities is not yet explained. The components of the overtone and double vibrational transition, like the QQ and S components of the fundamental, show no splitting or broadening with increasing density; these absorptions are believed to be due to quadrupole interactions while the QP and QR components of the fundamental are due to overlap interactions.

INFRARED ABSORPTION OF DEUTERIUM INDUCED BY INTERMOLECULAR FORCES

1965 ◽  
Vol 43 (5) ◽  
pp. 793-799 ◽  
Author(s):  
S. Paddi Reddy ◽  
C. W. Cho
Keyword(s):  
Absorption Band ◽  
Absorption Coefficient ◽  
Infrared Absorption ◽  
Room Temperature ◽  
Intermolecular Forces ◽  
Absorption Coefficients ◽  
Fundamental Band ◽  
Molecular Parameters ◽  
The Individual ◽  
Gas Pressures

The pressure-induced fundamental infrared absorption band of deuterium has been investigated in the pure gas for gas pressures up to 250 atm at room temperature. The binary and ternary absorption coefficients were determined from the integrated absorption coefficients of the fundamental band at different densities of the gas. The splitting of the Q branch into two well-resolved components QP and QR was observed; the contours also exhibit pronounced S(0) and S(2) components with an indication of the S(1) and O(2) components. The existing theory and the available molecular parameters of deuterium were used to calculate the binary absorption coefficients of the individual lines of the O and S branches and of the quadrupole part of the Q branch. From these calculations and the experimental value of the total binary absorption coefficient of the fundamental band, the overlap part of the binary absorption coefficient of the Q branch was estimated.

An analysis of the profile of the pressure-induced pure rotational spectrum of hydrogen gas

1969 ◽  
Vol 47 (1) ◽  
pp. 65-70 ◽  
Author(s):  
John W. Mactaggart ◽  
James L. Hunt
Keyword(s):  
Absorption Band ◽  
Frequency Shift ◽  
Line Profile ◽  
Power Law ◽  
Infrared Absorption ◽  
High Frequency ◽  
Frequency Region ◽  
Hydrogen Gas ◽  
Rotational Spectrum ◽  
Infrared Absorption Band

The pure rotational infrared absorption band of hydrogen has been investigated in the frequency region 500 to 1400 cm−1. Measurements have been made at densities of up to 100 amagat units and at temperatures of 298, 195, and 77 °K. A blue frequency shift, similar to the shift of the S(0) line observed by Bosomworth and Gush, of the S(1) line of 8 ± 3 cm−1 has been observed. An analysis of the profile has resulted in an individual S line profile which represents the high-frequency wing of the line by a "power law" rather than an exponential shape as presented previously by Bosomworth and Gush.

Simulations of high-resolution images of amorphous silicon films

1986 ◽  
Vol 44 ◽  
pp. 544-545
Author(s):  
G. Y. Fan ◽  
J. M. Cowley
Keyword(s):  
Electron Microscope ◽  
High Frequency ◽  
Fourier Transformation ◽  
Amorphous Materials ◽  
Low Frequency ◽  
Chromatic Aberration ◽  
Structure Information ◽  
Frequency Components ◽  
High Resolution Images ◽  
Spatial Frequency Spectrum

It is well known that the structure information on the specimen is not always faithfully transferred through the electron microscope. Firstly, the spatial frequency spectrum is modulated by the transfer function (TF) at the focal plane. Secondly, the spectrum suffers high frequency cut-off by the aperture (or effectively damping terms such as chromatic aberration). While these do not have essential effect on imaging crystal periodicity as long as the low order Bragg spots are inside the aperture, although the contrast may be reversed, they may change the appearance of images of amorphous materials completely. Because the spectrum of amorphous materials is continuous, modulation of it emphasizes some components while weakening others. Especially the cut-off of high frequency components, which contribute to amorphous image just as strongly as low frequency components can have a fundamental effect. This can be illustrated through computer simulation. Imaging of a whitenoise object with an electron microscope without TF limitation gives Fig. 1a, which is obtained by Fourier transformation of a constant amplitude combined with random phases generated by computer.

A Novel Adaptive PET/CT Image Fusion Algorithm

2019 ◽  
Vol 14 (7) ◽  
pp. 658-666
Author(s):  
Kai-jian Xia ◽  
Jian-qiang Wang ◽  
Jian Cai
Keyword(s):  
Lung Cancer ◽  
Image Fusion ◽  
High Frequency ◽  
Malignant Tumors ◽  
Low Frequency ◽  
Combination Method ◽  
Ct Image ◽  
Fusion Algorithm ◽  
Pet Ct ◽  
Frequency Components

Background: Lung cancer is one of the common malignant tumors. The successful diagnosis of lung cancer depends on the accuracy of the image obtained from medical imaging modalities. Objective: The fusion of CT and PET is combining the complimentary and redundant information both images and can increase the ease of perception. Since the existing fusion method sare not perfect enough, and the fusion effect remains to be improved, the paper proposes a novel method called adaptive PET/CT fusion for lung cancer in Piella framework. Methods: This algorithm firstly adopted the DTCWT to decompose the PET and CT images into different components, respectively. In accordance with the characteristics of low-frequency and high-frequency components and the features of PET and CT image, 5 membership functions are used as a combination method so as to determine the fusion weight for low-frequency components. In order to fuse different high-frequency components, we select the energy difference of decomposition coefficients as the match measure, and the local energy as the activity measure; in addition, the decision factor is also determined for the high-frequency components. Results: The proposed method is compared with some of the pixel-level spatial domain image fusion algorithms. The experimental results show that our proposed algorithm is feasible and effective. Conclusion: Our proposed algorithm can better retain and protrude the lesions edge information and the texture information of lesions in the image fusion.

Despeckling of Sar Images Using Shrinkage of Two-Dimensional Discrete Orthonormal S-Transform

2020 ◽  
pp. 2150023
Author(s):  
Priya R. Kamath ◽  
Kedarnath Senapati ◽  
P. Jidesh
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Relevant Information ◽  
Detection Algorithm ◽  
Two Dimensional ◽  
Sar Images ◽  
S Transform ◽  
Processing Step ◽  
Frequency Components ◽  
Shock Filter

Speckles are inherent to SAR. They hide and undermine several relevant information contained in the SAR images. In this paper, a despeckling algorithm using the shrinkage of two-dimensional discrete orthonormal S-transform (2D-DOST) coefficients in the transform domain along with shock filter is proposed. Also, an attempt has been made as a post-processing step to preserve the edges and other details while removing the speckle. The proposed strategy involves decomposing the SAR image into low and high-frequency components and processing them separately. A shock filter is used to smooth out the small variations in low-frequency components, and the high-frequency components are treated with a shrinkage of 2D-DOST coefficients. The edges, for enhancement, are detected using a ratio-based edge detection algorithm. The proposed method is tested, verified, and compared with some well-known models on C-band and X-band SAR images. A detailed experimental analysis is illustrated.

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