Showing papers on "Absorption (electromagnetic radiation) published in 1968"

Absorption Coefficients of Ozone in the Ultraviolet and Visible Regions

Abstract: The absorption coefficients of ozone have been measured in the ultraviolet and visible regions using essentially 100% pure ozone. The results confirm those of Inn and Tanaka in the ultraviolet, and those of Vigroux in the visible region.

A method of absorption correction by X-ray intensity measurements

Abstract: The theoretical and experimental principles of a method are described, which permits an approximate evaluation of the absorption correction by intensity measurements with the aid of a four-circle diffractometer.

Absorption parameters in electron diffraction theory

Abstract: Values of the parameter Vg/Vg are calculated for 100 kv electrons as a function of the reflection vector g for different crystal temperatures and for a number of different materials. It is shown that the usual assumption made, namely setting V0 ′ = Vg ′ = 0·1 Vg independent of g or material, is often a very poor approximation. Calculations based on the inelastic scattering mechanisms involved show that for a given value of g the ratio Vg '/Vg increases with increasing temperature and increasing atomic weight of the material. For a given temperature and material, Vg '/ g increases approximately linearly with g over a wide range of g values.

Uv, visible, and ir attenuation for altitudes to 50 km, 1968

Abstract: : An atmospheric attenuation model for the ultraviolet, visible, and infrared was developed in 1964, based on scattering (molecules and aerosols) and ozone absorption. Since then more measurements have been made and our knowledge of aerosol attenuation has widened. These circumstances result in attenuation model changes which are relatively unimportant for most exploratory calculations. In this paper the optical parameters are computed spectrally and with altitude as follows: (1) pure air attenuation parameters are determined by utilizing Rayleigh scattering cross sections with molecular number densities from the standard atmosphere; (2) ozone absorption parameters are derived based on Vigroux's coefficients applied to a representative atmospheric ozone distribution; (3) seven sets of aerosol measurements are compared and a profile of aerosol attenuation coefficients vs altitude is developed. Attenuation coefficients and optical thickness due to molecular, aerosol, and ozone attenuation are computed and tabulated individually so that the influence of each can be compared. The newly derived tabulations permit various exploratory calculations, including horizontal, vertical, and slat-path transmission at kilometer intervals to an altitude of 50 km, individually for each attenuating component or for overall atmospheric extinction (molecular + ozone + aerosol).

The effective attenuation in water of the gamma rays of gold 198, iridium 192, cesium 137, radium 226, and cobalt 60.

Abstract: The absorption and scatter of radiation in tissue alter the dose distribution around interstitial and intracavitary radioactive sources. Within the treated volume of an interstitial implant, the presence of tissue may cause the dose to vary as much as ±3 per cent from that anticipated with the same geometry in air. At more distant points, such as at the pelvic wall in the treatment for uterine cervix by intracavitary radiation sources, the absorption in tissue may reduce the dose by 10 to 15 per cent. With manual methods of calculation, the absorption and scatter corrections are usually ignored, but computer methods which have become available in the last few years usually include these corrections. There have been a number of determinations of the attenuation in water of the gamma rays of gold 198, iridium 192, cesium 137, radium 226 (in equilibrium with daughter products), and cobalt 60 (1–7). Calculations presented here, based upon the theoretical consideration of the diffusion of gamma rays in water b...

Optical study of the characteristics of shock-compressed condensed dielectrics

Abstract: CONTENTS Introduction 229 I. Study of the optical characteristics of shock-compressed condensed materials, and of the structure and smoothness of the fronts of large-amplitude shock waves 1. Experimental procedure 231 2. Front thickness and smoothness of shock waves in condensed inert and explosive substances 232 3. Density dependence of the refractive index of liquid dielectrics. Anomalous behavior of shock-compressed carbon tetrachloride 234 4. Investigation of the optical properties of shock-compressed ionic crystals. Nonequilibrium states 235 5. Optical study of elastoplastic waves in glass 237 6. Phase transition of water into ice VII under shock compression 238 II. Equilibrium radiation of the shock-wave front. Experimental determination of temperatures. 7. Possibility of temperature measurement in shock-compressed condensed materials. Principle of the method 240 8. Measurement of temperatures of shock-compressed ionic crystals and establishment of their melting curves for pressures up to 0.5-3 Mbar 241 9. Measurement of temperatures of shock-compressed lucite and carbon tetrachloride 245 III. Absorption of light by shock-compressed ionic crystals. Absorption and conduction mechanism. 10. Experimental determination of the absorption coefficient 245 11. Mechanisms of light absorption and conduction in shock-compressed ionic crystals 246 IV. Nonequilibrium radiation of shock-compressed ionic crystals 248 12. Nonequilibrium radiation at low temperatures. Electroluminescence of shock-compressed substances 248 13. Nonequilibrium radiation at high temperatures. Electronic screening of the radiation 249 References 251

The emission and absorption of waves by charged particles in magnetized plasmas

Abstract: A semiclassical theory describing the emission and absorption of waves is applied to the interaction of charged particles with waves in magnetized plasmas. Spontaneous emission of all cold plasma wave modes is calculated in detail. The method gives the absorption coefficient for the waves and a diffusion equation in momentum space for the particles describing the effects of the induced processes.

Effect of Particle Shape on the Spectral Absorption of Colloidal Silver in Gelatin

Abstract: Small prolate spheroids of silver (between 140 and 400 A av diam) were produced by photographic development of fine‐grain silver bromide embedded in gelatin. The shape and size distributions of the silver particles were determined from electron micrographs of thin sections. The average axial ratios of these spheroids had values for different preparations between 0.3 and 0.9. The optical absorption was measured and a shift of the main absorption peak (near 400 mμ) to shorter wavelengths, and of a secondary peak to longer wavelengths, with elongation of the particles was found to be in good quantitative agreement with the theory of Gans. The position of the main peak can be brought into even better agreement with the theory by taking account of the finite average particle size (by using the Mie theory) and by selecting the most appropriate set of optical constants for chemically prepared silver. Small departures from spherical shape affect the spectral absorption of colloidal silver much more than changes i...

Resonant absorption in the presence of faraday rotation.

Abstract: A general treatment of electro- and magneto-optical phenomena in the presence of resonant absorption is given. The resulting expressions in terms of the real and imaginary parts of a matrix index of refraction are easily utilized in calculations. We consider in detail the effects of these phenomena in M\"ossbauer experiments with polarized $\ensuremath{\gamma}$ rays, presenting expressions for absorption as a function of polarization as well as for the polarization of the transmitted beam, which are valid for arbitrarily thick absorbers. Comparisons with experimental data are presented.

Physical properties of a transition metal oxide: optical and photoelectric properties of single crystal and thin film molybdenum trioxide

Abstract: The optical absorption spectra of single crystals and thin films of MoO 3 have been measured in the temperature range 150 to 340 °K with polarized light. At room temperature, the absorption spectrum of a single crystal consists of two peaks at λ 4130 and λ 3930 A with E || C and only one absorption peak at 4250 A with E ⊥ C followed by a rapid rise in absorption. The temperature and frequency dependence of the absorption coefficient in the edge over a range of absorption magnitudes 10 2 -10 5 cm -1 are described by expressions of the form K(v, T) = K 0 exp[— (β/kT) (E 0 — hv )]. The temperature dependence of the absorption edge was found to be linear from 340 to 150 °K with a temperature coefficient of — 6.2 x 10 -4 and — 9.3 x 10 -4 eV/°K for E || C and E ⊥ C , respectively. The corresponding temperature co­efficients in thin films are — 2.7 x 10 -4 and —4.0 x 10 -4 eV/°K for E|| and ⊥ to the film surface, respectively. Measurements have been made of the refractive indices of a single crystal and thin films. Ultraviolet irradiation of a thin film of MoO 3 produces a broad colour centre band having a maximum at 8700 A. Several absorption peaks are resolvable in polarized light. On cooling down to 150 °K, the peak position shifts to shorter wavelength by 400 A (4.67 x 10 -4 eV/°K). An e. s. r. signal with g = 2.001 ± 0.005 has been observed in the colour film. The electrical conductivity has been measured on single crystals and polycrystalline samples in the temperature range 25 to 500 °C, and the activation energies are found to be 1.83 ± 0.01 eV (intrinsic) and 0.29 to 0.70 eV (extrinsic). Photoconductivity has been measured in single crystals and thin films as a function of photon energy, temperature, and irradiation intensity. Trapping plays a significant role in the conduction phenomena. The thermal activation energies associated with different trapping levels were determined from the photoconductive decay curves and the electrical glow peaks measurements and were found to be in the range 0.16 to 0.64 eV.

Selective Polarization of Light Due to Absorption by Small Elongated Silver Particles in Glass

Abstract: Polarizing glasses were made by stretching glass containing colloidal silver. The position of the absorption bands depends strongly on the elongation. This dependence seems to be consistent with the predictions of the theory of light absorption by small metal particles based on a free electron model.

Some optical properties of CuPd, AgPd, AuPd and CuMn, AgMn alloys

Abstract: Measurements of the transmission and reflection coefficients have been made on evaporated films of solid solutions of Pd in Cu, Ag and Au and Mn in Cu and Ag. In the ease of the Pd alloys additional absorption attributed to resonant bound states associated with the Pd d electrons has been observed. The location and breadth of these resonant levels have been determined for the Ag and Au alloys. In Cu the resonant state absorption overlaps the Cu absorption edge and is not separable. In the CuMn and AgMn alloys the bound d states of the Mn are known to be spin split. No evidence for the optical absorption due to these states has been found in CuMn which is interpreted as implying a very small splitting energy ∼0·25 ev per spin. Weak absorption is observed in the case of AgMn alloys and this is interpreted as indicating a spin splitting energy of ∼ 1 ev per spin. In all these alloys the absorption spectra of the matrix, particularly the characteristic edges of Cu, Ag and Au, are little affected by t...

Absorption of Infrared Radiant Energy by CO 2 and H 2 O. III. Absorption by H 2 O between 0.5 and 36 cm −1 (278 μ−2 cm)*

Abstract: Interferometric techniques have been employed to measure the H2O absorption between approximately 12.6 cm−1 and 36.0 cm−1. The experimental results, along with results obtained between 0.5 cm−1 and 10 cm−1 by other workers, have been compared with calculated values of transmittance based on theoretically determined positions, strengths, widths, and shapes of the absorption lines. From these comparisons it has become apparent that none of the well-known theoretical line shapes are correct for the extreme wings of the H2O lines below approximately 40 cm−1. The amount of continuum absorption which must be added to the theoretical absorption coefficient to provide agreement with the experimental results has been determined for N2- and self-broadened lines. A table of the line parameters has been included, along with a discussion of the procedure to be followed in calculating the transmittance of homogeneous and inhomogeneous paths.

Hydrogen bonding in water and ice

Abstract: The absorption bands due to the OH and OD stretching vibrations of HDO in ice were measured between 0 and −182° and compared with the corresponding bands in liquid water. Their frequencies were cor...

Optical Absorption by Polarons in Rutile (TiO2) Single Crystals

Abstract: The optical absorption in rutile single crystals doped with Nb and other impurities as well as partially reduced is investigated in the temperature range 10 to 900°K. It is shown that the spectrum and the magnitude of the optical absorption by current carriers can be satisfactorily explained in terms of the small polaron theory. The oscillator strength for the absorption band studied as well as the polaron binding energy, the mean electron-phonon coupling constant, and the nearest neighbour overlap integral are estimated from the experimental data.