Notes on Spectrophotometry

The source of light used as a background is an important factor in determining the convenience and accuracy of ultra-violet absorption work, etc. If a source of light of constant intensity is available, a direct comparison method can be used and it is only necessary to calibrate the plates. If the source of light is not constant in intensity, it is necessary to divide the light into two beams and use one to check the variations of intensity while the other goes through the absorbing substance or (during calibration) the reducing sector or wedge. This latter method requires much more complicated apparatus and if the variations in the source are at all large it becomes inaccurate. In addition to being constant in intensity a good background for ultra-violet absorption spectra should possess the following qualities:(1) Most of the energy should be emitted in the form of a continuous spectrum.(2) It is desirable to be able to use one photograph of the whole region to be investigated. For this purpose it is necessary that the variations of intensity in different parts of the spectrum should be small enough for it to be possible to arrange the exposure so that all parts of the spectrum are within the correct exposure range, i.e. it must not be necessary to over-expose any part in order to get a strong enough intensity at another wave-length.The hydrogen continuous spectrum possesses both these qualities and is an excellent background for the region on the short wave-length side of 3200 A.U. It may be used for longer wavelengths, but the hydrogen secondary lines are apt to prove trouble-some unless a fairly large dispersion is used.

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Note on vacuum grating spectroscopy

Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character ◽

10.1098/rspa.1920.0057 ◽

1920 ◽

Vol 98 (689) ◽

pp. 114-123 ◽

Cited By ~ 3

Keyword(s):

Wave Length ◽

Emission Spectra ◽

Ultra Violet ◽

Short Wave ◽

The Other ◽

Rapid Progress ◽

Other Hand ◽

Short Wave Length ◽

Grating Spectroscopy

In the spectroscopy of the extreme ultra-violet region, it is necessary to work either with arcs in vacuo or with sparks in one or other of the gases hydrogen or helium. As all other gases are opaque to ultra-violet radiations of short wave-length, their use is precluded. With many of the elements, arcs are difficult to maintain in a vacuum, and consequently one is driven to the use of sparks in either one or other of the two gases mentioned. Lyman, in his brilliant researches, has shown us that, with hydrogen, it is possible to obtain spectra extending to about λ 900 Å. U. For radiations below this limit, it would appear, however, that hydrogen is more or less absorbing.. With helium, on the other hand, the evidence available goes to show that this gas is transparent to radiations having wave-lengths as short as λ 400 Å. U. or λ 500 Å. U., and possibly shorter still. It would appear, then, that in the spectroscopy of the extreme ultra-violet, the procedure to be followed, which would permit of the most rapid progress being made, would be, in so far as the emission spectra are concerned, to work with a vacuum grating spectrograph, and to use an atmosphere of helium.

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The effects of ultra-violet rays upon the eye

Proceedings of the Royal Society of London. Series B, Containing Papers of a Biological Character ◽

10.1098/rspb.1912.0055 ◽

1912 ◽

Vol 85 (579) ◽

pp. 319-330 ◽

Cited By ~ 15

Keyword(s):

Ciliary Body ◽

Wave Length ◽

Radiant Energy ◽

Ultra Violet ◽

Inflammatory Lesion ◽

Short Wave ◽

Mercury Vapour ◽

Short Wave Length ◽

Body Positive ◽

The Media

In 1909 Messrs. J. Herbert Parsons and E. E. Henderson commenced some experiments on the action of short wave-length light on the lens and ciliary body, using Uviol glass mercury-vapour tubes and examining the lens and its capsule after exposure. To test for damage to the ciliary body too slight to be appreciable microscopically use was made of an observation of Römer’s, that in animals sensitised to the blood of another species, htemolysins were not transmitted from the blood to the aqueous unless the constitution of the latter were altered by a previous paracentesis or an inflammatory lesion of the iris and ciliary body. Positive results were obtained, but the experiments were not sufficiently extensive to be conclusive. I have, therefore, on behalf of the Committee of the Royal Society on Glassworkers’ Cataract, repeated and extended the experiments along lines suggested by Mr. Parsons. In the attempt to determine the effect of rays of various wave-lengths on the media of the eye, attention has been paid to three possible aetiological factors:—(1) The intensity of the light. (2) The part of the spectrum mainly represented in the source of light. (3) The possibility of the inclusion of electrolytic and mechanical as well as of radiant energy.

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III. On the spectrum of carbon

Proceedings of the Royal Society of London ◽

10.1098/rspl.1881.0123 ◽

1882 ◽

Vol 33 (216-219) ◽

pp. 403-410 ◽

Cited By ~ 1

Keyword(s):

Wave Length ◽

Ultra Violet ◽

Short Wave ◽

Accurate Data ◽

Emissive Power ◽

Spectroscopic Investigations ◽

Accurate Knowledge ◽

Short Wave Length

The spectroscopic investigations we have communicated to the Society “On the Reversals of the Lines of Metallic Vapours,” have shown the importance of a thorough and accurate knowledge of the ultra-violet spectra of the elements, for .it is in the lines of short wave-length as a rule that the greatest emissive power is manifested, and they are therefore most readily reversed. Thus we have succeeded in reversing upwards of 100 lines in the ultra-violet spectrum of iron (“Proc. Roy. Soc.,” vol. 32, p. 404). The necessity for accurate data in regard to this region of the spectrum led us to make a long study of the spectrum of magnesium, and the results of this investigation appeared in the volume of the “Proc. Roy. Soc.” just cited.

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Note on a connection between the visible and ultra-violet bands of hydrogen

Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character ◽

10.1098/rspa.1927.0065 ◽

1927 ◽

Vol 114 (769) ◽

pp. 643-650 ◽

Cited By ~ 3

Keyword(s):

Wave Length ◽

Ultra Violet ◽

Short Wave ◽

Short Wave Length ◽

The Many

The many lined spectrum of hydrogen on the short wave length side of λ 1675 Å was discovered by Schumann, and measured and extended by Lyman who published a list of wave-lengths of the lines in his book. A considerable number of the lines between 1025 and 1240 Å have been carefully measured recently by Werner who succeeded in arranging them into bands. Another system of bands in this region was discovered by Lyman in the spectrum of a discharge in argon which contained a trace of hydrogen. These bands, which it is convenient to call the Lyman bands, have recently been arranged by Witmer who has also measured up and reclassified some of Werner’s bands.

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V.—The Ionisation of Iodine Vapour by Ultra-Violet Light

Proceedings of the Royal Society of Edinburgh ◽

10.1017/s0370164600024895 ◽

1926 ◽

Vol 45 (1) ◽

pp. 34-41

Author(s):

W. West ◽

E.B. Ludlam

Keyword(s):

Quantum Theory ◽

Electron Impact ◽

Wave Length ◽

Ultra Violet ◽

Short Wave ◽

Ultra Violet Light ◽

Violet Light ◽

Negative Results ◽

Short Wave Length ◽

Effect Of Light

The ionisation of iodine vapour by light has been sought by several investigators with negative results. Nevertheless, the application of the quantum theory, which has proved so fruitful with respect to the relation between electron impact on gaseous molecules and the emission of light, leads to the expectation that the ionisation of a gas should be affected by light of sufficiently short wave-length. This ionisation was first observed by Lenard, who investigated the effect of light in the extreme ultra-violet on air and other gases.

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The absorption spectra of the halogen acids in the vacuum ultra-violet

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1938.0128 ◽

1938 ◽

Vol 167 (929) ◽

pp. 216-227 ◽

Cited By ~ 60

Keyword(s):

Absorption Spectra ◽

Wave Length ◽

Emission Spectra ◽

Ultra Violet ◽

Short Wave ◽

Molecular Ions ◽

Alkyl Halides ◽

Short Wave Length ◽

Continuous Absorption ◽

Continuous Background

Although the halogen acids have long been known to Possess regions of continuous absorption, no discrete electronic spectra have previously been reported for the neutral molecules. Their emission spectra occurring between 2800 and 4000 A really belong to the molecular ions. In the work to be described here, new absorption spectra of the halogen acids, which consist of very intense system of relatively discrete bands, have been dis-covered in the Schumann region. The spectra are essentially in the nature of strong resonance bands and are very similar in this respect to corresponding bands of the alkyl halides (price 1936). Extensive absorption systems of I 2 , Br 2 and Cl 2 have also been found in the same region. These will be described in a later publication. The continuous background against which the bands were observed was provided by the Lyman continuum. Other experimental details have been reported previously (Collins and Price 1934). The absorption spectrum of hydrogen iodide is shown in fig. 1 a (Plate 11). This particular photograph corresponds to a pressure of about 0·01 mm. in a path length of 50 cm. The most striking feature of the spectrum is the presence of a large number of bands with strong sharp Q branches accompanied on either side by weaker P and R branches (fig. 1 a, b, c ), the rotational structures of allied are only slightly degraded. This indicates that a relatively non-bonding electron is being excited, a fact which is also substantiated by the absence of any pronounced vibrational progressions. For example, the first strong band at 1762 A is unaccompanied by any vibrational bands, there doing a transparent region more than 5000 cm. -1 wide to the short wave-length side of it. Though the rotational structures of the P and R branches of this band are diffuse, the sharp nature of the Q branch is easily discernible (see fig. 1 a, c). The spectra of HBr and HCl each begin with a very similar band occurring at 1491 A for HBr (fig. 1 d ) and at 1331A for HCl (fig. 1 e ). It will be shown that these bands are related to one another and are analogous to the B bands of the alkyl halides. The next strong bands on the short wave-length side of them can further be linked with the C bands of the alkyl halides. Because of certain peculiarities which the above bands of the halogen acids (fig. 1 c, d, e ) exhibit, they will be discussed together in a later paragraph.

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On the absorption of light by crystals

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1938.0137 ◽

1938 ◽

Vol 167 (930) ◽

pp. 384-391 ◽

Cited By ~ 153

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".

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

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1937.0195 ◽

1937 ◽

Vol 162 (911) ◽

pp. 451-479 ◽

Cited By ~ 82

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.

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

Baghdad Science Journal ◽

10.21123/bsj.4.3.387-392 ◽

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.

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