Gas adsorption on clean metal surfaces may be studied by observing the change in work function of the surface as adsorption proceeds. A photoelectric technique for following these changes by measuring the photocurrent...
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Gas adsorption on clean metal surfaces may be studied by observing the change in work function of the surface as adsorption proceeds. A photoelectric technique for following these changes by measuring the photocurrent excited by two spectral lines is developed, and a graphical method of analysis of the results is given. This method has the advantage of being much quicker than other photoelectric techniques such as the determination of the retarding-potential characteristic, and may thus be applied to the study of more rapid adsorption processes. As examples of its use, the method has been applied to a study of the adsorption of oxygen and water vapor on films of aluminum evaporated under conditions of ultrahigh vacuum. The work function of the clean aluminum films was 4.27 eV. For small oxygen exposures (up to about 10 18 molecules cm −2 ) the work function of the contaminated aluminum decreased by about 0.05 eV; for larger exposures (up to about 10 20 molecules cm −2 ) the work function increased by about 0.05 eV. Water vapor adsorption causes a reduction in the work function by more than 1 eV for an exposure of about 10 19 molecules cm −2 .
Variable background from alloy to alloy in direct reader analysis of stainless steels affects working curves adversely Spectrographic evidence shows that its effect can be photometrically removed Its influence can be ...
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Variable background from alloy to alloy in direct reader analysis of stainless steels affects working curves adversely Spectrographic evidence shows that its effect can be photometrically removed Its influence can be minimized by use of excitation producing a “black burn” using argon shielding of the analytical gap in a point-to-plane arrangement. Automatic dynamic background correction is accomplished with production instruments based on a method of Weekley and Norris.
In dealing with optical imaging systems, it is more feasible experimentally to measure line spread functions than point spread functions. When the intensity distribution is known to possess rotational symmetry, the po...
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In dealing with optical imaging systems, it is more feasible experimentally to measure line spread functions than point spread functions. When the intensity distribution is known to possess rotational symmetry, the point spread function can be obtained mathematically from the corresponding line spread function by solving an integral equation. A direct solution of this equation is given which represents a procedure that is simpler for practical use than the usual one involving Fourier transforms.
The algebraic method for the determination of higher-order aberration coefficients based on the notion of quasi-invariance employs a process of iteration in which the n th step yields the exact coefficients of order 2...
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The algebraic method for the determination of higher-order aberration coefficients based on the notion of quasi-invariance employs a process of iteration in which the n th step yields the exact coefficients of order 2 n +1. To carry out the n th step one requires at each surface (i) all p and q coefficients of order less than 2 n +1, (ii) the set of intrinsic p coefficients of order 2 n +1 (the latter depending solely on the surface in question and not upon the coefficients which describe the imperfections implicit in that part of the system which precedes it). The algebraic steps leading to the explicit forms of higher-order intrinsic coefficients are quite elementary but very tedious and lead to an almost unmanageable jungle of terms unless a suitable reduction is carried out once and for all. The secondary terms have been dealt with elsewhere. The present paper now throws the monochromatic tertiary (i.e., seventh order) intrinsic coefficients of spherical surfaces into a very simple form eminently suitable for computation with an ordinary desk machine. In fact, the ten unbarred intrinsic coefficients, which alone appear in a suitably constructed computing scheme, require a total of only thirteen entries per surface.
If we are given the spectrophotometric curves of a color and three colorants to be used in matching it, the computation of the concentrations of the three colorants required for a tristimulus match is a complicated no...
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If we are given the spectrophotometric curves of a color and three colorants to be used in matching it, the computation of the concentrations of the three colorants required for a tristimulus match is a complicated nonlinear problem. However, with the help of an approximating assumption, a linear solution may be obtained by a matrix inversion technique. Although this is an approximate solution, it is better the less meta-meric the match. With this rough solution as a starting point, iteration may be used to approach an exact match to any desired degree of accuracy. The inverted matrix used for the iterative computation is identical to that used for the rough solution.
In aerial photography the airplane’s ground speed introduces image movement during the exposure. To reduce its influence on the image quality, it is possible to apply a shorter exposure time but only at the cost of u...
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In aerial photography the airplane’s ground speed introduces image movement during the exposure. To reduce its influence on the image quality, it is possible to apply a shorter exposure time but only at the cost of using a more sensitive film. This introduces a higher granularity and, because most details are of low contrast, another reduction of the image quality. Obviously, there is an optimum choice for any particular situation. A fast analysis of such problems is carried out on the “ITC Modulation Transfer Board”. From the modulation transfer functions of lens, emulsion, and image movement, together with other data, the smallest detail visible is determined. The Systems Engineering shows that the higher MTF does not necessarily correspond to the best choice of parameters. This paradox can be understood only by considering the granularity of the films used.
The special techniques required to measure the photographic transfer functions defined in Part I are described, and detailed methods of computation are given. A photographic procedure for separating isotropic optical ...
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The special techniques required to measure the photographic transfer functions defined in Part I are described, and detailed methods of computation are given. A photographic procedure for separating isotropic optical losses into lens and film components is discussed; results of this method are compared with data obtained by different methods at other laboratories. Illustrative measurements of both optical and chemical transfer functions are presented for several different emulsions and processing techniques. These data are consistent with the model proposed in Part I and with microdensitometer traces of “knife-edge” exposures. It is indicated that the term “adjacency effects” should be abandoned in favor of the more general formulations used here.
methods of computation are described for determination of the refractivity of air from measurements made with a corner-reflector Michelson interferometer. Results are given for eleven vacuum wavelengths from 7034 to 2...
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methods of computation are described for determination of the refractivity of air from measurements made with a corner-reflector Michelson interferometer. Results are given for eleven vacuum wavelengths from 7034 to 20 587 A. These results support Svensson’s conclusion that Edlen’s dispersion formula may be increased in precision by raising it slightly in the near-infrared. They indicate however an increase of 0.12×10 −8 ×(3.35 μ −2 − σ 2 ) over Svensson’s formula. A question is raised as to the existence of appreciable variations, perhaps seasonal in nature, in the refractivity of outdoor air.
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