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.

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 The spectrum of H 2 : The bands analogous to the ortho-helium line spectrum

1929 ◽  
Vol 122 (790) ◽  
pp. 688-718 ◽  
Keyword(s):  
Preliminary Investigation ◽  
Rotational Quantum Number ◽  
Principal Series ◽  
Visible Spectrum ◽  
Ultra Violet ◽  
Line Spectrum ◽  
Final States ◽  
Combination Principle ◽  
S States

In “Structure in the Secondary Spectrum of Hydrogen—Part V” it was shown that there existed in this spectrum a very extensive series of bands whose null lines were related by a Rydberg-Ritz formula and whose electronic terms were very close to those of the principal series of the so-called helium doublets (orthohelium) showing that the spectrum of H 2 is closely analogous to the line spectrum of He. [It is also very similar to the spectrum of He 2 .] This similarity has since been confirmed by the discovery and investigation of the absorption spectrum of unexcited H 2 by Dieke and Hopfield from which it appears that none of the final 2 states of that spectrum, in which the transitions are from 1 1 S to an upper 2 state, are the same as the final 2 states of these emission bands. On the other hand their 2 1 S states do agree, to the accuracy of the ultra-violet data, with the final states of an entirely different set of band systems in the visible spectrum which are therefore analogous to the parhelium spectrum. The conclusions of Part V were drawn from a study of the Q branches of the bands only. In an earlier paper (Part IV) a preliminary investigation of some of the accompanying P and R branches had been made by a study of the intensity distribution in these bands in the first type discharge. This method enables the lowest rotational quantum number lines of the bands to be picked out with some certainty but the upper lines cannot in general be recognised on account of the faintness of the discharges. These can only be located by finding lines which satisfy some reasonable combination principle. An attempt made by one of us (O. W. R.) in collaboration with Dr. D. B. Deodhar to extend the classification of Part IV led us to the conclusion that the existing data were inadequate, mainly owing to insufficient resolution, to enable a satisfactory decision to be formed as to whether the details of Part IV were correct or ought to be modified.

scholarly journals IX. Wave-length determinations and general results obtained from a detailed examination of spectra photographed at the solar eclipse of January 22, 1898

1901 ◽  
Vol 197 (287-299) ◽  
pp. 381-413 ◽  
Keyword(s):  
Solar Eclipse ◽  
Focal Length ◽  
Wave Length ◽  
Visible Spectrum ◽  
Ultra Violet ◽  
Detailed Examination

The results are here given of a detailed study and measurement of a series or ten spectra, photographed by me with a small prismatic camera, at the eclipse camp of the British Astronomical Association stationed at Talni, India. The instrument referred to had an aperture of 50 millims., and a focal length of about 890 millims. It wTas fitted with two crown-glass prisms, each of 60° angle, placed in front of an ordinary visual objective, the component lenses of which were slightly separated in order to shorten the focus of the ultra-violet rays relatively to those of the visible spectrum.

scholarly journals V. On the spectrum, visible and photographic, of the great Nebula in orion

1890 ◽  
Vol 46 (280-285) ◽  
pp. 40-60 ◽  
Keyword(s):  
Royal Society ◽  
Wave Length ◽  
Visible Spectrum ◽  
Ultra Violet ◽  
Bright Line

I have added the name of Mrs. Huggins to the title of the paper, because she has not only assisted generally in the work, but has repeated independently the delicate observations made by eye In the year 1882 I had the honour to lay before the Royal Society a note on the photographic spectrum of this nebula, in which I described a new bright line in the ultra-violet, to which I gave a wave-length of about 3730. In addition to this new line, the lines of hydrogen, H β and H γ , which I had discovered by eye in my early observations on the visible spectrum, were to be seen upon the plate.

scholarly journals PHOTOSENSITIZATION OF ANIMALS AFTER THE INGESTION OF BUCKWHEAT

1928 ◽  
Vol 47 (6) ◽  
pp. 1013-1028 ◽  
Author(s):  
Charles Sheard ◽  
Harold D. Caylor ◽  
Carl Schlotthauer
Keyword(s):  
Wave Length ◽  
Visible Spectrum ◽  
Ultra Violet ◽  
Mercury Vapor ◽  
Malignant Neoplasms ◽  
Absorption Bands ◽  
Quartz Mercury ◽  
Degree Of Sensitization ◽  
The Common ◽  
Mercury Vapor Lamp

The chief points presented in this paper are: 1. Following the ingestion of buckwheat (plant or seed) varicolored guinea pigs, white swine and goats exhibited symptoms of photosensitization, the degree of sensitization being in the order given. 2. Rabbits, dogs, white mice and rats did not manifest symptoms of photosensitization. 3. The symptoms and reactions were: agitation, itching, scratching of the ears, weakness, urticaria with sloughing and symptoms similar to those in anaphylaxis. 4. Microscopic examinations showed the lack of marked pathologic change. The lesions, such as petechial hemorrhage of the lungs, brain, liver, stomach and kidneys, suggest that profound toxemia has been present. 5. Lesions were not found which appeared to be suggestive of malignant neoplasms. 6. Irradiation by a quartz mercury vapor lamp apparently develops a resistance to photosensitization, probably because of increased pigmentation induced by ultra-violet light. 7. From the nature of the physiologic and pathologic reactions produced under various filters and from a consideration of the percentages of transmission of solar energy in the visible spectrum, it would seem that the region of photosensitization lies between 580 millimicrons (yellow) and the red end of the spectrum. This conclusion, moreover, is substantiated by the fact that irradiation by a quartz mercury vapor lamp (which radiates no energy in the visible spectrum at a wave-length greater than 579 millimicrons) produces no symptoms or reactions. 8. Spectrophotometric determinations of alcoholic extracts of grass (non-toxic) and of buckwheat (toxic) show the presence of two additional bands in the absorption spectrum of buckwheat with maxima at about 540 and 600 millimicrons, respectively, together with the common absorption zones at 430 to 490 millimicrons and 630 to 690 millimicrons. 9. Spectrophotometric determinations of blood serums of sensitized animals show, besides the usual absorption bands peculiar to oxyhemoglobin (with maxima at 540 and 580 millimicrons respectively), two zones with maxima at 600 and 660 millimicrons respectively. 10. The fluorescence of chlorophyll per se, as suggested by previous investigators, is not, in all probability, the cause of the sensitization induced by buckwheat. 11. Hematoporphyrine is not the photodynamic substance in all probability. 12. Phylloporphyrine may be the photodynamic substance. In this regard, also, the possibility of cholehematin is not to be ruled out.

scholarly journals THE RELATION OF TIME, INTENSITY AND WAVE-LENGTH IN THE PHOTOSENSORY SYSTEM OF PHOLAS

1928 ◽  
Vol 11 (5) ◽  
pp. 657-672 ◽  
Author(s):  
Selig Hecht
Keyword(s):  
Absorption Spectrum ◽  
Reaction Time ◽  
Absorption Spectra ◽  
Wave Length ◽  
Visible Spectrum ◽  
Ultra Violet ◽  
Fundamental Properties ◽  
Stimulation Of ◽  
The Way

The most effective point in the visible spectrum for the stimulation of Pholas is 550 mµ. On the red side, the effectiveness drops rapidly to almost zero. On the violet side, the effectiveness drops to about half, and rises again in such a way as to indicate a possible second maximum in the near ultra-violet. On the basis of certain ideas these data are assumed to represent the properties of the absorption spectrum of the photosensitive system in Pholas. A comparison with Mya shows that the absorption spectra of the photosensitive systems in the animals are distinctly different. Nevertheless the way in which intensity and reaction time are related in the two animals are found to be identical. The conclusion is then drawn from this and from previous work, that although the fundamental properties of the photoreceptor process show an identical organization in several different animals, the materials which compose these processes are specific.

scholarly journals On the dispersion of gaseous mercury, sulphur, phosphorous, and helium

1908 ◽  
Vol 80 (540) ◽  
pp. 411-419 ◽  
Keyword(s):  
Focal Plane ◽  
Wave Length ◽  
Visible Spectrum ◽  
Refractive Indices ◽  
Gaseous State ◽  
Light Passing ◽  
Gaseous Mercury

In continuation of previous work on the refractive indices of certain elements in the gaseous state, we have measured the dispersion of the elements named above within the limits of the visible spectrum. Jamin’s refractometer was used, and the arrangement of the instrument was that described in our previous paper. But, as different wave-lengths had to be employed for the determination of the dispersion, the method of illumination was improved. Light from a Nernst filament was focussed on the slit of one of Messrs. Hilger and Co.’s fixed-deviation spectroscopes, and, in the focal plane of the resulting spectrum, a slit was placed capable of motion in that plane. The adjustment was calibrated by comparing the wave-length of the light passing through the slit with the reading of the drum of the spectroscope. By rotating the drum, light of any required wave-length could be obtained, and, by narrowing the slits, the spectrum was of sufficient purity to admit of two hundred bands being counted to one-fifth of their breadth.

scholarly journals An improved method of ultra-violet anomalous rotary dispersion of sodium tartrate

1928 ◽  
Vol 119 (783) ◽  
pp. 706-709
Keyword(s):  
Wave Length ◽  
Visible Spectrum ◽  
Ultra Violet ◽  
Rotatory Power ◽  
Rotatory Dispersion ◽  
Improved Method ◽  
Sodium Tartrate ◽  
Approximate Form ◽  
Rotary Dispersion ◽  
In Series

A large number of ultra-violet polarimetric measurements have been made by a method described by one of us in 1908.* In this method a triple-field polarimeter, with Foucault in place of Nicol prisms, is arranged in series with a quartz or quartz-calcite spectrograph. A quartz-calcite lens, replacing the eyepiece of the polarimeter, casts a real image of the triple field on the slit of the spectrograph, and thus gives rise to a triply divided spectrum, intersected by dark bands. The wave-length corresponding with a given rotation is determined by finding a line which is of equal intensity in the three fields. The approximate form of the curve of rotatory dispersion can be determined by setting the analyser in a series of positions separated by 5° or 10° ; but it is then advisable to “bracket” some of the more conspicuous lines by making fresh exposures at intervals of perhaps 0·2°, when the rotation corresponding with the wave-length of a given line can be determined within about 0·1°. This degree of accuracy is less than that which can be reached in the central part of the visible spectrum, where the readings may be reproduced under favourable conditions within about 0·01° ; but it is not appreciably less than the accuracy of visual readings in the red and violet regions, and for many purposes is quite satisfactory. Thus, with a column of quartz 496 mm. in length, readings to 1° sufficed to give the rotatory power in degrees per milli­metre within 0·002°, corresponding with an error of about 1 part in 100,000 at wave-length 2327. The present investigation was undertaken in order to find out whether the same apparatus could be used to record with sufficient accuracy the much smaller rotations of solutions which had been largely diluted, in order to render them transparent in a region near to (or covered by) an absorption band. For this purpose the concentration is often reduced to I per cent. : the observed rotations may then be of the order of 0·5°, and must be read to 0·01° or less in order to give a true impression of the form of the curve of rotatory dispersion.

scholarly journals The absorption spectrum of lithium vapour

1930 ◽  
Vol 129 (810) ◽  
pp. 354-360 ◽  
Keyword(s):  
Absorption Spectrum ◽  
Wave Length ◽  
Principal Series ◽  
Ultra Violet ◽  
Normal Pressure ◽  
Steel Tube ◽  
Quartz Spectrograph ◽  
High Boiling Point ◽  
Estimated Error ◽  
Low Dispersion

The absorption spectrum of lithium vapour has been previously studied under low dispersion by several workers. There are two main features of interest in it, the principal series, extending from the first line in the red at 6708 A. to a limit at 2299 A., and the band structures in the blue-green, 4500─5500 A. and in the red 6800─7700 A. The observation of the spectrum is attended by two principal difficulties: first, lithium has a high boiling point in the neighbourhood of 1400° C. at normal pressure, and it is strongly corrosive at high temperatures; secondly, the limit of the series has a very low wave-length, this fact rendering it very difficult to use a source not peculiarly rich in ultra-violet light for the transmission of continuous radiation through the vapour. Bevan, the first worker to publish any data* relating to this spectrum, heated lithium in a double-walled steel tube and used as illuminant a condensed cadmium spark; he used a quartz spectrograph and measured the wave-lengths of the first 41 members of the principal series with estimated error 0·2─0·3 A., deriving a Hick’s formula for their wave-numbers.

scholarly journals On spectrophotometry in the visible and ultra-violet spectrum

1921 ◽  
Vol 99 (696) ◽  
pp. 78-84 ◽  
Keyword(s):  
Visible Spectrum ◽  
Ultra Violet ◽  
Wave Number ◽  
Previous Knowledge ◽  
Present Communication ◽  
Stellar Spectra ◽  
Extended Sources ◽  
Central Strip ◽  
Dispersing System ◽  
Considerable Loss

In a previous communication the use of the neutral wedge for the determination both of the photographic and absolute intensities of spectrum lines has been discussed, and the results of its application to the study of certain phenomena relating to the spectra of hydrogen and helium have been given. The method has been found to be simple and convenient for the study of the relative intensities and of the structure of broadened lines in the visible spectrum. There are, however, certain features of the method which under some circumstances limit its application; in particular the density of the “neutral” wedge increases with the wave-number, and for the investigation of the ultra-violet down to λ = 2000 A, the method is at present inapplicable. Although it might be possible to construct wedges of crown glass with a very small angle for use in the ultra-violet, the fact that a number of such wedges would be required for different ranges would destroy the principal advantage of the method. Whilst no special precautions are required in the investigation of extended sources of light, it is evident that when small sources of light are used it is of the utmost importance to ensure that that portion of the slit which is behind the wedge is uniformly illuminated before the wedge is put into position, and in the case of selected regions of a source of light, e. g. , the spectrum from a particular point in the electric arc, it is only possible to obtain correct results by means of devices which entail a very considerable loss of light. The present communication relates to a method which, whilst not superior to the wedge method in accuracy, has the advantage that it can be used in any part of the spectrum which can be photographed through quartz lenses and prisms, and its application to the extreme ultra-violet beyond λ = 2000 A should present no serious difficulty. The method consists in crossing the dispersing system, e. g. , the prism of the spectrograph, with a very coarse grating, and reducing the length of the slit to a very small value. The grating is inserted between the prism and the camera lens of the spectrograph with the rulings perpendicular to the refracting edge of the prism, and a continuous spectrum thus appears on a plate as a dark central strip with a succession of other strips of different intensities on either side, the intensities of these orders being determined by the ruling of the grating and the width of the strips by the length of the slit. In the case of a discontinuous spectrum the "lines” are found to consist of dots of different intensities on either side of the central dot. It is evident that if the last dots which are just visible in the case of two lines are noted, a previous knowledge of the relative intensities of the different orders corresponding to these dots at once enables the relative intensities of the lines to be determined. It will be noted that the fact that the slit is reduced to a point not only enables different regions of a light source to be investigated without difficulty, but suggests a further application, which will be considered later, in the study of stellar spectra.

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