THE THEORY OF OPTICAL ABSORPTION IN ALKALI METAL CRYSTALS

1934 ◽  
Vol 10 (3) ◽  
pp. 335-341
Author(s):  
W. H. Watson
Keyword(s):  
Absorption Band ◽  
Optical Absorption ◽  
Alkali Metal ◽  
Lattice Constant ◽  
Wave Length ◽  
Ultra Violet ◽  
Periodic Lattice ◽  
Free Electrons ◽  
Sodium Potassium ◽  
Upper Limit

The experimental results of R. W. Wood are compared with theory using the model of free electrons perturbed by the periodic lattice potential. All relevant data are collected in a table in which it is seen that in sodium, potassium, rubidium and caesium the wave-length of the upper limit of the absorption band in the visible and near ultra-violet is proportional to the square of the lattice constant, while lithium occupies an anomalous position. The facts at present available do not permit a completely definite test of the absolute values of these wave-lengths given by the theory.

scholarly journals Dispersion of light by Potassium Vapour

1910 ◽  
Vol 84 (570) ◽  
pp. 209-225 ◽  
Keyword(s):  
Wave Length ◽  
Principal Series ◽  
Visible Spectrum ◽  
Ultra Violet ◽  
Anomalous Dispersion ◽  
Present Communication ◽  
Absorption Region ◽  
Sodium Potassium ◽  
Light Passing ◽  
Quantitative Results

Anomalous dispersion in the region of the red lines of potassium was first observed by Ebert in 1904. The method adopted for Ebert’s experiments was a modified form of the crossed prism method used by Wood in the investigation of the corresponding phenomena in the case of sodium. Potassium was heated in a tube through which two currents of hydrogen passed from each end to a central outlet. The cool hydrogen kept the potassium vapour in a prismatic form, so that light passing along the length of the tube suffered deviation and dispersion by the potassium vapour prism. The author of the present communication has shown that there is no need for the hydrogen streams. If the tube be kept cool on its upper surface the metallic vapour takes of itself a prismatic form or is arranged in layers of decreasing density, and so behaves in a similar way to a prism of homogeneous vapour. The present communication deals with quantitative results from the measurement of dispersions at different wave-lengths, and it appears that the deviation due to potassium vapour is observable over the whole of the visible spectrum and for a considerable distance in the ultra-violet. Strong absorption takes place at the lines of the principal series and for wave-lengths near these series lines we have "anomalous" dispersion. This phenomenon has been observed at seven of the pairs forming the principal series lines for potassium—as the pairs of lines in this series get closer and closer together with diminishing wave-length, the dispersion effects after the first two pairs are only observable outside the lines forming a pair, but there appears a lack of symmetry in the observed dispersion curves corresponding to the different intensities of the lines forming the pair. The dispersion to be observed may then be regarded as that corresponding to the principal series absorption lines; no other absorption region seems to affect the dispersion —at any rate at low densities of vapour.

scholarly journals On the ultra-violet absorption of crystalline preparations of vitamin B 1

1933 ◽  
Vol 113 (780) ◽  
pp. 48-56 ◽  
Keyword(s):  
Biological Activity ◽  
Absorption Band ◽  
Wave Length ◽  
Monochromatic Light ◽  
Ultra Violet ◽  
Vitamin B ◽  
Pyrimidine Derivatives ◽  
Main Band ◽  
Vitamin Activity ◽  
Hydrion Concentration

Evidence has been produced by several workers tending to support the view that vitamin B 1 possesses an ultra-violet absorption band with a maximum at about 260 mμ. Bowden and snow (1932) stated that the preparation studied by them possessed such a band, which disappeared simultaneously with the vitamin activity on irradiation with monochromatic light of wave-length 25 mμ. The absorption curve published by Windaus et al . (1931) for their preparations also showed a maximum near 260 mμ. Heyroth and Loufbarrow (1932) have studied a large number of preparations of varying vitamin activity, and have shown that much of their ultra-violet absorption can be attributed to inactive purine and pyrimidine derivatives. Nevertheless, they conclude that there is a significant correlation between absorption at 260 mμ and biological activity (see also Ohdake, 1932). It is therefore somewhat surprising that the preparations recently made at Oxford (Kinnersley, O'Brien and Peters (1932-1933), which can claim to be the most potent yet produced, have their maximum absorption at a definitely different wave-length, namely 245-9 muμ, while at 260 mμ their absorption curves only show a barely perceptible hump, protruding from the steeply descending portion of the main band. An attempt to connect this discrepancy with a possible effect of hydrion concentration on the wave-length of the maximum led to the discovery of a curious phenomenon.

scholarly journals I. Notes on the absorption of ultra-violet rays by various substances

1883 ◽  
Vol 35 (224-226) ◽  
pp. 71-74 ◽  
Keyword(s):  
Absorption Band ◽  
Continuous Spectrum ◽  
Rock Salt ◽  
Wave Length ◽  
Ultra Violet ◽  
Induction Coil ◽  
Iron Electrodes ◽  
In Cells

The following notes contain some records of ultra-violet absorptions in addition to those which have been examined by Soret, Hartley, M. de Chardonnet, and other investigators. For these observations we have generally used the spark of an induction coil, with Leyden jar, between iron electrodes as the source of light. Occasionally we have used other electrodes, but the lines of iron are so multitudinous, and so closely set in a large part of the ultra ­violet region of the spectrum, that they form almost a continuous spectrum, at the same time there are amongst them a sufficient number of breaks and conspicuous lines to serve as points of reference. The spectroscope has a single prism of quartz, and the telescopes have quartz lenses. The image of the spark was projected on to the slit of the spectroscope by a quartz lens, and the absorbent substances were interposed between the slit and the last-mentioned lens. The gases were held in tubes fitted, some with quartz, others with rock salt, plates on the ends; liquids in cells with quartz sides. The spectra were all photographed. Chlorine in small quantity shows a single absorption band extending from about N (3580) to T (3020). As the quantity of chlorine is increased this band widens, expanding on both sides, but rather more rapidly on the less refrangible side. Different quantities of chlorine produced absorption from about H (3968) to wave-length 2755, from wave-length 4415 to 2665, and from wave-length 4650 to 2630. With the greatest quantity of chlorine tried the absorption did not extend above wave-length 2550.

scholarly journals On the effect of temperature on the anomalous reflection of silver

1925 ◽  
Vol 107 (742) ◽  
pp. 247-254 ◽  
Keyword(s):  
Wave Length ◽  
Ultra Violet ◽  
Total Reflection ◽  
Effect Of Temperature ◽  
Free Electrons ◽  
Frequency Increase ◽  
Restoring Force ◽  
A Value ◽  
Anomalous Reflection ◽  
Electro Magnetic

It has long been known that the reflection coefficient of silver, besides minishing steadily in the ultra-violet, shows a marked anomaly in the ighbourhood of wave-length 3,200 Å, sinking to a value of nearly zero, while either side of this point it amounts to about 50 per cent. The cause of is phenomenon is unknown, though from the classical electro-magnetic int of view it would naturally be regarded as some kind of "resonance" ect; that is to say, that the “free” electrons cannot, for some reason, brate with frequencies corresponding to this region; for the bound ctrons, though they could, if they were in resonance with frequency, increase e total reflection, could hardly decrease it, as actually occurs. If this is so, and if the restoring force on the vibrating electrons varies with e distance between them and the neighbouring atoms and electrons, it may expected that the limiting frequency on either side of this band will vary the metal contracts or expands. A change in the temperature of the silver ould then produce a corresponding shift in the position of the band of weak flection, and measurement of the amount of this shift may afford some ue to the nature and magnitude of the forces which act upon the “free” ectrons.

SYNTHESIS AND SPECTROSCOPY OF SOME QUATERNARY OXYFLUORIDE GLASSES DOPPED WITH COPPER

2013 ◽  
Vol 22 ◽  
pp. 284-291 ◽  
Author(s):  
CH. SRINIVASU ◽  
M. A. SAMI ◽  
A. EDUKONDALU ◽  
SYED RAHMAN
Keyword(s):  
Optical Absorption ◽  
Absorption Spectra ◽  
Copper Ions ◽  
Wave Length ◽  
Broad Band ◽  
Spin Hamiltonian Parameter ◽  
Band Gap Energy ◽  
Site Symmetry ◽  
Optical Absorption Spectra ◽  
Absorption Data

Electron paramagnetic resonance (EPR) and optical absorption spectra of copper ions in xLiF-(50-x)Li2O-20SrO-30Bi2O3 glass system have been studied. MDSC studies showed that the glass transition temperature decreases with LiF content. Optical absorption spectra of the pure glasses reveled that the cut off wave length increased and optical band gap energy decreased with increase in LiF content. EPR spectra of all the glass samples exhibit resonance signals characteristic of Cu2+ ions. The Cu2+ ions are in well-defined axial sites but subjected to small distortion leading to the broadening of the spectra. The spin-Hamiltonian parameter values indicate that the ground state of Cu2+ is d x2 y2 and the site symmetry around Cu2+ ions is tetragonally distorted octahedral. The optical absorption spectra exhibited a broad band corresponding to the d-d transition bands of Cu2+ ion. By correlating EPR and optical absorption data, the bond parameters are evaluated from various techniques.

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