scholarly journals The continuous absorption of light in potassium vapour

1943 ◽  
Vol 181 (987) ◽  
pp. 386-399 ◽  
Keyword(s):  
Atomic Absorption ◽  
Ultra Violet ◽  
Effective Length ◽  
Absorption Process ◽  
Molecular Absorption ◽  
Continuous Absorption ◽  
Exchange Effects ◽  
Absorption Of Light ◽  
New Type ◽  
Vacuum Ultra Violet

A new type of absorption tube for the study of metal vapours is described. It is shown how the effective length of the absorbing column may be calculated. Measurements of the continuous absorption in potassium vapour, extending into the vacuum ultra-violet, are described. A separation of the atomic and molecular absorption is effected. At short wavelengths the atomic absorption appears to increase rapidly, and varies linearly with the frequency. The value of the absorption coefficient at the series limit is 1·2 (± 0·3) x 10 -20 cm. 2 . The results for the atomic absorption are in conflict with theory. It is suggested that exchange effects are operative in the absorption process and may account for the discrepancy.

scholarly journals Exchange effects in the absorption of light. I. Ca and Ca +

1941 ◽  
Vol 177 (970) ◽  
pp. 329-340 ◽  
Keyword(s):  
Matrix Element ◽  
Transition Matrix ◽  
Continuous Wave ◽  
Transition Matrix Element ◽  
Wave Functions ◽  
Absorption Coefficients ◽  
Continuous Absorption ◽  
Exchange Effects ◽  
Absorption Of Light ◽  
Theory And Experiment

The continuous absorption coefficients of normal Ca and Ca + are calculated. Both the discrete and continuous wave functions used in the calculation include the effect of electron exchange. Comparison is effected with results obtained neglecting exchange and it is found that appreciable modifications are introduced by its inclusion. This is particularly true for Ca + which is a sensitive case owing to very strong interference in the integrand of the transition matrix element. The bearing of the results on the calculation of absorption coefficients in general is discussed, and it is pointed out that the discrepancy between theory and experiment for potassium arises because this also is a very sensitive case. An application of the results for Ca is made to resolve a discrepancy between determinations of interstellar electron densities carried out using different methods by Strömgren and Struve.

Absorption cross-sections in the vacuum ultra-violet. - I. Continuous absorption of oxygen (1800 to 1300 Å)

1953 ◽  
Vol 220 (1140) ◽  
pp. 61-70 ◽  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Ultra Violet ◽  
Absorption Cross ◽  
Absorption Spectrophotometry ◽  
Maximum Value ◽  
Continuous Absorption ◽  
The Cross ◽  
Quantitative Absorption ◽  
Vacuum Ultra Violet

Absorption cross-sections for oxygen in the region 1670 to 1360 Å, corresponding to the process O 2 3 Ʃ g - + hv → O( 3 P ) + O( 1 D ), have been measured. The cross-section has a maximum value of 1⋅81 x 10 -17 cm 2 at 1450 Å and falls to half-value at 1567 and 1370 Å. The paper includes an account of technical methods of quantitative absorption spectrophotometry in this part of the vacuum ultra- violet.

Absorption cross-sections in the vacuum ultra-violet III. Methane

1955 ◽  
Vol 229 (1176) ◽  
pp. 44-62 ◽  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Wave Length ◽  
Ultra Violet ◽  
Photoionization Cross Section ◽  
Absorption Cross ◽  
Continuous Absorption ◽  
Length Range ◽  
Photo Ionization ◽  
Vacuum Ultra Violet

Cross-sections for the continuous absorption of radiation by methane in the wave-length range 1600 to 350A have been measured. The absorption is analyzed so as to distinguish between absorption leading to photo-dissociation processes and absorption due to photoionization. The main photo-ionization process is CH 4 +hv->CH 4 + -e - , and the photoionization cross-section is measured for free electron energies from 0 to about 20 eV. Little evidence is found for processes such as CH 4 + hv-> CH 2 + H+e - The results are compared with calculations by Dalgamo. The paper includes an account of the technique of photographic spectrophotometry in the region 1100 to 200A.

scholarly journals On the absorption of light by crystals

1938 ◽  
Vol 167 (930) ◽  
pp. 384-391 ◽  
Keyword(s):  
Absorption Spectrum ◽  
Wave Length ◽  
Short Wave ◽  
Point Of View ◽  
Theoretical Point ◽  
Lattice Vibrations ◽  
Short Wave Length ◽  
Continuous Absorption ◽  
Absorption Of Light ◽  
Positive Hole

The purpose of this paper is to discuss the absorption of light by non-metallic solids, and in particular the mechanism by which the energy of the light absorbed is converted into heat. If one considers from the theoretical point of view the absorption spectrum of an insulation crystal, one finds that it consists of a series of sharp lines leading up to a series limit, to the short wave-length side of which true continuous absorption sets in (Peierls 1932; Mott 1938). In practice the lattice vibrations will broaden the lines to a greater of less extent. When a quantum of radiation is absorbed in the region of true continuous absorption, a free electron in the conduction band and a "positive hole" are formed with enough energy to move away from one another and to take part in a photocurrent within the crystal. When, however, a quantum is absorbed in one of the absorption lines , the positive hole and electron formed do not have enough energy to separate, but move in one another's field in a quantized state. An electron in a crystal moving in the field of a positive hole has been termed by Frenkel (1936) an "exciton".

Vacuum ultra-violet spectroscopic ellipsometry study of sputtered BeZnO thin films

Optik ◽  
2011 ◽  
Vol 122 (22) ◽  
pp. 2050-2054 ◽  
Author(s):  
Jebreel M. Khoshman ◽  
Martin E. Kordesch
Keyword(s):  
Thin Films ◽  
Spectroscopic Ellipsometry ◽  
Ultra Violet ◽  
Vacuum Ultra Violet

The absorption spectrum of SO and the flash photolysis of sulphur dioxide and sulphur trioxide

1959 ◽  
Vol 249 (1259) ◽  
pp. 498-512 ◽  
Keyword(s):  
Absorption Spectrum ◽  
Dissociation Energy ◽  
Sulphur Dioxide ◽  
Flash Photolysis ◽  
Ultra Violet ◽  
Vibrationally Excited ◽  
A Value ◽  
Continuous Absorption ◽  
Sulphur Trioxide ◽  
Normal Spectrum

The flash photolysis of sulphur dioxide under adiabatic conditions results in the complete temporary disappearance of its spectrum , which then slowly regains its original intensity over a period of several milliseconds. Simultaneously with the disappearance of the sulphur dioxide spectrum a continuous absorption appears in the far ultra-violet and fades slowly as the sulphur dioxide reappears. It is shown that the effect of the flash is thermal rather than photochemical, and the possibility of the existence of an isomer of sulphur dioxide at high temperatures is discussed; the disappearance of the normal spectrum on flashing is explained in this way. Several previously unrecorded bands of SO observed in the photolysis indicate that the vibrational numbering of its spectrum should be revised by the addition of 2 to the present values of v' . This leads to a value of the dissociation energy of 123.5 kcal. In formation about the levels v' = 4, 5 and 6 has also been obtained. The isothermal flash photolysis of sulphur trioxide results in the appearance of vibrationally excited SO, and the primary photochemical step in this reaction is discussed.

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