The Effect of Temperature Upon Certain Absorption Spectra

Kasson Stanford Gibson

Cornell University, 1916 - Absorption spectra - 47 pages

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Page 27 - Jt as indicated. Precautions were taken to prevent dust from settling on the inside of the Dewar in the path of the light beam or upon the specimen during the observations. Also it was found necessary, in order to prevent condensation of moisture from the air on the outside of the Dewar, to fasten heating coils on each side about the places where the light entered and left. The source of light used was an acetylene flame L whose pressure was kept constant by means of a water manometer. The light...‎

Page 29 - Fig. 2. Glass No. i. Cd, Se. Variation of the per cent, transmission P and of the coefficient of absorption K with wave-length X at the temperatures — 180°, —80°, +20", 100°, 210°, 320° and 430° C. was taken at —60° instead of —80° C. The values for 20° are the average of the values taken just before heating, and just before cooling. The cooling effect was studied about a year after the heating effect. In Fig. 2 all the curves are numbered. In the other figures curves I and 7 only...‎

Page 28 - ... the screw. If these three did not agree closely, more were taken. This was almost always necessary at the red and violet ends of the spectrum. If the average of the settings with the specimen in position is D, and the setting with the specimen removed is / (taken from the calibration curve), then DjI is the per cent, of the incident light transmitted. But since about 4 per cent, of the light incident on each surface of the glass is reflected at that surface, the true per cent, transmission P...‎

Page 26 - ... asbestos paper, which prevented an excessive loss of heat by radiation. A piece of mica at each end prevented air currents and thus helped to keep the temperature on the inside steady. All temperatures were measured by means of a copper-advance thermo-j unction which was inserted as indicated at J\. This was used in the usual way with a potentiometer. It was calibrated by taking readings at the known temperatures of o° and 100°, and at 232°, 327.5° and 419° C., the melting points of tin,...‎

Page 26 - APPARATUS. These glasses were ground in the shape of circular discs about 22 mm. in diameter and from one to two mm. thick. The faces were highly polished and made parallel to within .01 mm. These precautions were found necessary in order to obtain the same and therefore the correct per cent, transmission when the specimen was moved around in its position. To study the effect of heating, the glass N (Fig. i) was placed between two iron washers and heated in the furnace H. A thin cylindrical shell...‎

Page 47 - ... the wave-length at different temperatures. 2. The wave-lengths of the various lines and bands in the absorption spectrum have been determined. These values check closely with those obtained by other investigators. 3. A relation has been found between the wave-length X and the absolute temperature T for an absorption doublet in the red part of the spectrum. This relation is of the form X = a + bekT, where a, b and k are constants which may be determined graphically. The writer wishes to express...‎

Page 28 - Kx, log i/P = Kx, where x is the thickness of the glass specimen. In computing K, the values of log i/P were taken from a curve plotted between P and log i/P. RESULTS. In Figs. 2 to 9, the results of the investigation are shown graphically. In Figs. 2 to 6, the values of P, the per cent, transmission and of K, the coefficient of absorption are plotted against wave-lengths for various temperatures. In each figure, both for P and for K, there are seven curves corresponding to the following temperatures,...‎

Page 32 - Glasses Nos. 3 and 4. Variation of the coefficient of absorption K with temperature T at certain wave-lengths. cooling no change at all was found in the room temperature curves. The biggest changes occur on the edge of the general absorption region, .5 X Fig. 9. Glasses Nos. I to 4. Variation of the coefficient of absorption K with wave-length A at the extreme temperatures, — 180° and 430°, only. and this results in some cases in a shift of the point of maximum per cent. transmission as can be...‎

Page 47 - ... the wave-length 6900, as found, is the mean wave-length of the two lines corresponding to the natural frequencies of the resonators of the active material; ie, the wave-length corresponding to the frequencies which these resonators would possess if uninfluenced by the surrounding molecules of A12O3 composing the crystal. If that be true, the additional wave-length of 22 or 23 Angstrom units at absolute zero might be considered as due to the decrease in frequency of the resonators, brought about...‎

Page 30 - EFFECT OF TEMPERATURE UPON ABSORPTION. 199 In Figs. 7 and 8, values of K are plotted against temperature T for those wave-lengths which show the greatest changes. These curves are Fig. 4. Glass No. 3. Cd, Se. Variation of the per cent, transmission P and of the coefficient of absorption K with wave-length X at the temperatures — 180°, —95°, +20°, 100°, 210°, 320° and 430° C. for specimens Nos. i to 4 as indicated. In Fig. 9 are plotted values of K at the extreme temperatures, — 1 80°...‎

Bibliographic information

• Title: The Effect of Temperature Upon Certain Absorption Spectra
• Author: Kasson Stanford Gibson
• Publisher: Cornell University, 1916
• Original from: the University of Michigan
• Digitized: Oct 2, 2007
• Length: 47 pages