scholarly journals The absorption of light in caesium vapour in the presence of foreign gases

1936 ◽  
Vol 157 (890) ◽  
pp. 66-79 ◽  
Keyword(s):  
Wave Length ◽  
Short Wave ◽  
Theoretical Explanation ◽  
Random Errors ◽  
Short Wave Length ◽  
Absorption Of Light ◽  
Hydrogen Deuterium ◽  
Photometric Technique ◽  
Empirical Generalizations ◽  
Small Alteration

The absorption of caesium vapour on the short wave-length side of the series-limit, alone, and in the presence of helium, has been described in earlier papers. It was shown that helium, at a pressure of a few centi metres of mercury, greatly reduced the absorption at all wave-lengths and also produced significant changes in the shape of the absorption curve. No theoretical explanation of these results has been given. At this stage of the investigation it appeared more desirable to obtain measurements of moderate accuracy on a number of gases, rather than to attempt very detailed and accurate measurements on one other gas. The present paper contains results on the absorption of caesium in the presence of the following gases:—neon, argon, krypton, xenon, nitrogen, hydrogen, deuterium, and benzene. All these gases give effects qualitatively similar to those produced by helium. It is still not possible to give a detailed theory of the results, but some empirical generalizations emerge from the extensive data now available. Experimental The methods used for the control of temperature were similar to those previously described. The photometric technique was the same except for one small alteration. In the experiments on the absorption of caesium in the presence of helium, the absorption was measured by comparison with certain grids. The reduction of light produced by these grids had previously been measured and they were used in the experiments on the absorption of caesium in vacuum. Some of the present experiments were carried out in this way, but in the later experiments the absorption of caesium in the presence of the foreign gas was compared more directly with the absorption of caesium in vacuum, by recording both kinds of absorption spectra on the same plate. Suitable calibration spectra were also included. This direct comparison eliminated the possibility of systematic errors due to imperfect temperature control, etc. It also reduced the effect of random errors.

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".

scholarly journals The absorption of light by the coloured globules in the retina of the domestic hen

1929 ◽  
Vol 105 (738) ◽  
pp. 371-374 ◽  
Keyword(s):  
Scattered Light ◽  
Wave Length ◽  
Visible Spectrum ◽  
Short Wave ◽  
Alternative View ◽  
Short Wave Length ◽  
Full Explanation ◽  
Absorption Of Light ◽  
Specific Receptors ◽  
Domestic Hen

Schultze (1866) pointed out that the coloured globules in the retinæ of birds might afford a means wherby stimulation of the cones would be restricted to certain regions of the visible spectrum (7). A few other investigators have ascribed sensual discrimination of colour to retinal filters situate in front of the specific receptors fro light (1, 4 and 6). An alternative view (2, 3) regards the coloured globules as decreasing, merely generally and relatively unselectively, i. e. , quantitatively rather than qualitatively, the amount of light of short wave-length which reaches the sensitive (outer) limb of the cones. This might possibly be useful by reducing the amount of the more highly scattered light and so might improve the visibility of distant objects (2). This, however, can hardly be the full explanation, for if the function of the coloured globules be merely to reduce the amount of the more refrangible end of the spectrum the various globules need not be of more than one colour.

scholarly journals Continuous absorption of light in cæsium vapour

1934 ◽  
Vol 143 (849) ◽  
pp. 472-481 ◽  
Keyword(s):  
Wave Length ◽  
Principal Series ◽  
Short Wave ◽  
Main Difficulty ◽  
Absorption Cell ◽  
Absorption Tube ◽  
Short Wave Length ◽  
Continuous Absorption ◽  
Absorption Of Light ◽  
Photo Ionization

A region of continuous absorption lying on the short wave-length side of the limit of the principal series and corresponding to the photo-ionization of the atom is to be expected in the alkali metal vapours. The currents due to photo-ionization have been measured and several attempts have been made to observe the absorption. The main difficulty is in the action of the vapour on the windows of the absorption cell. This has usually been overcome by keeping the ends of the absorption tube cool and checking the diffusion of the vapour from the centre of the tube by means of a foreign gas. This gas produces a large and complicated effect on the absorption (Harrison). In the present experiments it has been found possible to avoid the use of a foreign gas by employing a long absorption tube and a low vapour pressure. Cæsium was used because it gives a sufficient pressure at a moderate temperature and because its series limit lies in the most convenient region of the spectrum.

The absorption of light by thallium vapour on the short wave-length side of the series limit

1954 ◽  
Vol 224 (1156) ◽  
pp. 83-90 ◽  
Keyword(s):  
Cross Section ◽  
Wave Length ◽  
Theoretical Work ◽  
Short Wave ◽  
Broad Line ◽  
Absorption Cross ◽  
Sharp Line ◽  
Short Wave Length ◽  
Absorption Of Light ◽  
The Continuum

Measurements of the absorption of light in thallium vapour from the series limit at 2030 to 1450Å are described. The absorption cross-section at the series limit is 4∙5 ± 0∙8 × 10 -18 cm 2 and the f -number for the continuum over the range of the experiment is 0∙025 ± 0∙005. Auto-ionization lines are observed at 2007, 1610 and 1490Å in agreement with those reported by Beutler & Demeter (1934 b ). The moderately sharp line at 2007Å ( 2 P 0 ½ → 4 P 3/2 ) has an f -number of 0∙005 ± 0∙001 and a lifetime of 18 ± 5 × 10 -15 s, while the broad line at 1610Å ( 2 P 0 ½ → 2 D 3/2 ) has an f -number of 0∙52 ± 0∙09 and a lifetime of 2∙2 ± 0∙1 × 10 -15 s. The 1490Å line ( 2 P 0 ½ → 2 P ½ ) is sharp and the f -number is estimated to be of the same order as that of the line 2007Å. These results are discussed in relation to the auto-ionization selection rules and previous experimental and theoretical work is reviewed.

scholarly journals The absorption of light in cæsium vapour in the presence of helium

1935 ◽  
Vol 150 (870) ◽  
pp. 478-486 ◽  
Keyword(s):  
Spectral Region ◽  
Wave Length ◽  
Short Wave ◽  
Short Wave Length ◽  
Absorption Of Light

In a recent paper we have described measurements of the absorption of light by cæsium vapour in the spectral region on the short wave-length side of the series limit. In the present work we examine the effect of the addition of a foreign gas on this absorption. Helium was used in a first investigation because, for reasons given below, we expected its effects to be simpler in interpretation than those of most other gases. Besides its intrinsic importance the work is of interest because a filling gas has been used to check the diffusion of the vapour in many experiments on absorption in metal vapours and the effect of these additional gases was quite unknown. Although helium has not been much used for this purpose, it seemed to be a suitable substance to use as a filling gas in future experiments.

scholarly journals The Bakerian lecture —Regularities and irregularities in the ionosphere—I

1937 ◽  
Vol 162 (911) ◽  
pp. 451-479 ◽  
Keyword(s):  
Specific Conductivity ◽  
Wave Length ◽  
Ground Level ◽  
Short Wave ◽  
The State ◽  
Total Conductivity ◽  
The Sun ◽  
Magnetic Studies ◽  
Short Wave Length ◽  
Radio Measurements

Our knowledge concerning the state of the atmosphere lying above about 80 km. in height has been derived from experiments on radio wave reflexion as well as from studies of terrestrial magnetism and of the aurora. The information derived from radio experiments is, fortunately, in the nature of a supplement to, rather than a duplicate of, information derivable in other ways. As one of the best examples in this connexion may be mentioned the question of electrical conductivity. Here the magnetic studies of Schuster and Chapman yield an estimate of the total conductivity for currents travelling horizontally, whereas the radio measurements give the state of ionization at different levels from which the specific conductivity at those levels may be estimated. One of the most striking things about the ionosphere is the marked solar control. Speaking generally it may be said that the ionization increases and decreases as the sun rises and sets. Again, speaking generally, we may say that the main part of the ionization is caused by solar-violet light. The rays from the sun meet the outer layers of the atmosphere first and the short wave-length radiation is absorbed there, causing ionization. It thus comes about that the study of the ionosphere becomes the study of an interesting part of the sun's spectrum which cannot be detected at ground level. It also becomes the study of certain atomic processes such as photo-ionization, recombination of ions and attachment of electrons to neutral molecules such as cannot be investigated at very low pressure in the laboratory, because of the influence of the walls of the vessel confining the gas.

scholarly journals Study the Effect of solvent on the Optical Properties Performance of active polymeric laser media

2007 ◽  
Vol 4 (3) ◽  
pp. 387-392
Author(s):  
Baghdad Science Journal
Keyword(s):  
Absorption Spectrum ◽  
Pure Water ◽  
Wave Length ◽  
Blue Shift ◽  
Short Wave ◽  
Fluorescence Yield ◽  
Effect Of Solvent ◽  
Long Wave ◽  
Short Wave Length ◽  
Laser Media

The paper include studies the effect of solvent of dye doped in polymeric laser sample which manufactured in primo press way, which is used as an active (R6G) tunable dye lasers. The remarks show that, when the viscosity of the solvent (from Pure Water to Ethanol), for the same concentration and thickness of the performance polymeric sample is increased, the absorption spectrum is shifts towards the long wave length (red shift), & towards short wave length (blue shift) for fluorescence spectrum, also increased the quantum fluorescence yield. The best result we obtained for the quantum fluorescence yield is (0.882) with thickness (0.25mm) in Ethanol solvent in concentration (2*10-3mole/liter), while when we used the Pure Water as a solvent, we found that the best quantum fluorescence yield is (0.72) at the same thickness & concentration of the sample.

The Results of Astroclimate Observations in the Short-Wave Length Interval of the Millimeter-Wave Range on the Suffa Plateau

2017 ◽  
Vol 59 (8-9) ◽  
pp. 763-771 ◽  
Author(s):  
G. M. Bubnov ◽  
Yu. N. Artemenko ◽  
V. F. Vdovin ◽  
D. B. Danilevsky ◽  
I. I. Zinchenko ◽  
...  
Keyword(s):  
Millimeter Wave ◽  
Wave Length ◽  
Short Wave ◽  
Short Wave Length ◽  
Millimeter Wave Range ◽  
Wave Range

Die Beeinflussung der Zellkerne in den Vorkeimen von Dryopteris filix-mas durch rote und blaue Strahlung

1963 ◽  
Vol 18 (7) ◽  
pp. 557-562 ◽  
Author(s):  
Rainer Bergfeld
Keyword(s):  
Protein Synthesis ◽  
Visible Light ◽  
Blue Light ◽  
External Factor ◽  
Wave Length ◽  
Red Light ◽  
Three Dimensional ◽  
Short Wave ◽  
Nuclear Volume ◽  
Short Wave Length

Morphogenesis and differentiation of fern gametophytes (Dryopteris filix-mas) are strongly controlled by light. “Normal” morphogenesis, i. e. formation of two- or three dimensional prothallia, can occur only under short wave length visible light (= blue light). In darkness and under long wave length visible light (= red light) the gametophytes will grow as filaments. The blue light dependent photoreactive system which controls morphogenesis seems to be located in the outer layers of the cytoplasm. The control of morphogenesis is causally connected with the increase of protein synthesis under the influence of blue light.In the present paper the influence of red and blue light on shape and volume of the nucleus in the fully grown basal cell of the young gametophyte of Dryopteris filix-mas has been investigated. In blue light the nuclei are more or less spherical, in red and in darkness they are spindle shaped. If the light quality is changed the shape of the nuclei is only slightly influenced; the nuclear volume, however, is drastically changed: increase of volume in the blue, decrease of nuclear volume in red and darkness. These reversible changes of nuclear volume under the influence of light, which are apparently correlated with changing rates of protein synthesis, are an impressive example for the control of nuclear properties by an external factor via the cytoplasm.

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