Interaction of Slow Electrons with Insulating Crystals. I. Absorption Coefficient for Cleaved Alkali Halides; Experimental Techniques

1961 ◽  
Vol 32 (5) ◽  
pp. 860-866 ◽  
Author(s):  
C. J. Cook ◽  
William J. Fredericks
Keyword(s):  
Absorption Coefficient ◽  
Alkali Halides ◽  
Experimental Techniques ◽  
Slow Electrons

The Absorption Coefficient for Slow Electrons in Gases

1930 ◽  
Vol 35 (10) ◽  
pp. 1217-1225 ◽  
Author(s):  
C. E. Normand
Keyword(s):  
Absorption Coefficient ◽  
Slow Electrons

Experimental Techniques

2006 ◽  
Author(s):  
Michael E. Thomas
Keyword(s):  
Absorption Coefficient ◽  
Spectral Response ◽  
Broad Band ◽  
Index Of Refraction ◽  
Experimental Techniques ◽  
The Real ◽  
Complex Index ◽  
Optical Propagation ◽  
Bulk Absorption ◽  
Complex Index Of Refraction

This chapter presents basic experimental techniques and various apparatus for measuring the complex index of refraction and related quantities. Generally, measurements of transmittance, reflectance, and emittance are made using spectrometers or lasers. Other important techniques, which measure directly the real refractive index, n, the absorption coefficient, βabs , and the scattering coefficient, βsca, such as interferometry, ellipsometers, calorimetry, and scatterometers, are also introduced. Ultimately, experimental procedures must be taught in the laboratory. Thus, devoting only one chapter to experimental technique and five to theory is not indicative of the importance of this fundamental topic. By discussing the measurement of basic optical parameters, it is intended that the concepts developed in the first five chapters will be reinforced. All of the theoretical models developed in the previous chapters contain measurable parameters. Basic theory often helps guide the design of a good experiment. Once data is available, it can be used to check the assumptions of the theory. This interplay between experiment and theory is an essential part of definitive work. The chapter has two main parts; the first covers measurements of the real and imaginary parts of the complex index of refraction and the second covers measurements of scattering. As established in Chapter 2, the characterization of bulk absorption mechanisms on optical propagation is accomplished by the complex index of refraction. Considerable effort was expended in Chapters 3, 4, and 5 to obtain models of the complex index. Thus, at this point, we wish to find ways to experimentally measure the complex index of refraction for various media. The broad-band spectral response of a medium is commonly measured by a spectrometer. There are two main types of spectrometers, dispersive and interferometric. Generally, spectrometers make broad-band transmission, emission, and reflection measurements, and therefore indirectly measure, n̄. Interferometric measurements, are the exception. Lasers, which feature narrow-band, high-intensity, highly directional light are often used to complement and calibrate broad-band spectrometer measurements. The highest accuracy measurements of the absorption coefficient are obtainable by laser techniques, which can directly measure the components of the complex index.

scholarly journals The absorption coefficient for slow electrons in mercury vapour

1929 ◽  
Vol 125 (796) ◽  
pp. 134-142 ◽  
Keyword(s):  
Absorption Coefficient ◽  
Path Length ◽  
Mean Free Path ◽  
Mercury Vapour ◽  
Cross Sectional ◽  
Original Apparatus ◽  
Maximum Angle ◽  
The Mean ◽  
Slow Electrons ◽  
Good Agreement

The effective cross-sectional area of an atom is defined in this paper as that area within which a passing electron is deflected so that it can no longer go through a system of slits defining a beam of electrons. The sum of all these areas in a cubic centimetre of the gas defines the absorption coefficient, the reciprocal of which is the mean free path. The absorption coefficient is a function of the atom studied and the velocity of the electron. It way also depend on the geometry of the apparatus which defines the maximum angle of deflection. From the agreement of the results obtained by several observers with different limiting angles, the variation of the observed absorption coefficient with size of the limiting angle appears to be small. The absorption coefficient is compound from the equation I = I 0 e -α xp , where I is the electron current at the end of the path, I 0 the current at the beginning of the path, x the path length, p the pressure of the gas α the absorption coefficient. Apparatus .—For the measurement of the absorption coefficient a modification of Ramsauer's original apparatus was used. The same modification was previously used for the measurement of the absorption coefficient in other gases giving results in good agreement with those by Ramsauer's more complicated apparatus.

Sign in / Sign up

Export Citation Format

Share Document