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Evidence for energy transfer from Dy+3 to Tb+3 ions in CaF2 is presented. Emission spectra and decay-time measurements are described and discussed.

Une condition essentielle pour pouvoir aligner des atomes ou des ions par pompage optique est que la vitesse de pompage doive etre comparable a la vitesse de relaxation dans l'etat fondamental. Des temps de relaxation de l'ordre de [FORMULE] sec ont ete mesures sur quelques ions paramagnetiques, a l'etat solide meme a la temperature ordinaire : les temps les plus longs ont ete trouves dans le cas des ions dont l'etat fondamental n'a pas de moment angulaire orbital. Pour les ions dont les spectres d'absorption dans le visible et dans l'ultraviolet sont les mieux connus, les forces d'oscillation correspondent a des valeurs de l'ordre de [FORMULE], ce qui est insuffisant. L'ion Europium divalent, d'etat fondamental [FORMULE] possede une bande d'absorption vers 3 380 A dont la force d'oscillation est de l'ordre de [FORMULE]. Ceci pourrait suffire pour obtenir une vitesse de pompage satisfaisante. Le manganese divalent, etat [FORMULE] phosphorescent dans le sulfure de zinc possede des bandes d'absorption d'une force d'oscillation de l'ordre de l'unite. Mais ces bandes sont situees dans l'ultraviolet extreme. Les auteurs sont en train de faire des essais pourobtenir des effets de pompageoptique dans Eu ++.

Experiments have been performed in order to ascertain the factors affecting the lifetime of an rf excited, internal reflector, helium‐neon laser oscillating at λ6328 A. Using the results of the experiment it has been found possible to make practical lasers of simple design having lifetimes of over 1000 h operation. This performance has been achieved by improving the reflectors and by adjusting discharge conditions and gas filling to optimum.

Studies of the energy transfer process at room temperature in the doubly doped system Cr, Nd Yt3Al5O12 are reported The efficiency of the transfer process was measured by comparing the fluorescent intensities of Cr3+ and Nd3+ ions in crystals with a variety of doping levels and also by studying the time decay of the Cr3+ emission. From a comparison of the results it appears that transfer to Nd3+ ions occurs predominantly from the 2E Cr3+ state. The overall enhancement of Nd3+ emission due to transfer from Cr3+ ions was also measured when exciting the ions with unfiltered light from a tungsten-iodine lamp.

The infrared spectrum in the range 3000–50 cm−1and the Raman spectrum of solutions of dithiophosgene have been obtained. There are no coincidences in the infrared and Raman spectra, and the only structure consistent with this and approximately tetrahedral carbon valencies is[Formula: see text]that is tetrachloro-1,3-dithietane, in which the ring is planar or nearly planar. A tentative assignment of the observed bands is given on the basis of D2hsymmetry.

Some absorption lines of rare-earth ions in calcium fluoride were found to be considerably affected by irradiation with x rays. These narrow lines, which appeared superimposed on a broad background of color-center absorption, were in some cases over 100 times stronger after irradiation and had strongly asymmetric line shapes, often resulting in an antiresonance dip. It is proposed that these effects are caused by interaction of the rare-earth ion and a neighboring color center.

Raman spectra have been obtained for molten and solid Ga2Cl4 and mixtures with Ga2Cl6 in which the compound Ga3Cl7 is formed. It is shown that Ga3Cl7 and KGa2Cl7 have the constitution M+Ga2Cl7– in the solid state. Solutions of gallium in molten Ga2Cl4 give, in addition to the GaCl4– spectrum, an extra Raman band at 235 cm–1, close to the most intense band of Ga2Cl62–.

The Raman spectrum of the complex InCl3,2Et3O just above the melting point indicates that both ether molecules are co-ordinated to indium and that the InCl3 unit is planar. Characteristic frequencies due to internal vibrations of the ligands are similar to previously observed frequencies in the complex of aluminium chloride with diethyl ether.

This nucleus was identified in four cats, four dogs and nine human spinal cords, but was not identifiable in seven other human specimens. In all three species the nucleus extends rostrally into the lower third of the medulla. Cell measurements of the perikarya yielded a mean diameter of 34.1 μ in the dog, 26.7 μ in the cat, and 15.7 μ in man. Nuclear diameters as well as the nucleus-cytoplasm and volume ratios were determined. The lateral cervical nucleus is considered to be rudimentary in man and was a well-defined structure in only 2 of 16 specimens. In one of these two cases a total of 5173 cells were counted in the nuclei of both sides at the C1 and medullary levels. The pertinence of these observations to the preservation of tactile sensation after injury of the dorsal columns in man, is discussed.

The ions Ga2X62–(X = Cl, Br, or I), which contain a metal–metal bond and probably have ethane-like structures, are formed when gallium dissolves in halogen acids and have been isolated as crystalline Me4N+ salts.

Low-frequency i.r. and Raman spectra of InCl3,2Et2O, InBr3,2Et2O, InCl3,2Et2S, and InBr3,2Et2S are given and interpreted in terms of D3h skeletal symmetry.

The mean lifetime of the 4F3/2 level of Nd3+ in LaF3 has been determined as a function of concentration. The sample dimensions are found to affect the results.

Sample establishments in the metal industries of the West Midlands conurbation are classified according to the number and function of their material linkages with other establishments. Three industries are examined and compared: ironfoundry, dropforgings and lock and latch production. Multivariate ordination techniques are employed to assess the combined influence of various linkages, and to identify different arrays of local and non-local connection. The extent of local agglomeration is therefore also identified in terms of the complexity of local plant linkage. This participation of industrial establishments in the local linkage system is then correlated with independently identified organizational attributes, including employment size, category of ownership, the technical processes employed and the principal product markets which are served. Local linkage appears to be related to the organizational form and size of individual plants, acting to some extent independently of their product categories. The spatial organization of manufacturing is thus shown to be one aspect of its more general organizational characteristics, suggesting that an understanding of one is important for the appreciation of the other. BOTH of the authors of this paper have quite recently been involved in a published discussion of the nature and significance for locational studies of 'industrial linkage'.' Such linkage we define to include all of the operational contacts, including flows of material and exchanges of information, between the separate functional elements of the manufacturing system. Although the relevant 'elements' may be regarded as whole industries or sectors of the economy (as in input-output studies2), this paper focuses on the locational attributes of particular plants and the manner in which production processes may be organized between them. At this scale we are concerned with industrial organization as it affects the interdependence of locationally separate establishments, both through ties of ownership and, more generally, through convenient commercial arrangements. In the past, only partial views of industrial linkage have been put forward. When describing the important features of 'horizontal', 'vertical' and 'diagonal' linkage, P. S. Sargant Florence3 was attempting to explain the logic of industrial 'swarming' in the case of the West Midlands metal industries. R. C. Estall and R. O. Buchanan,4 who relied heavily on the analysis of Sargant Florence, clearly associated the significance of linkage with industrial agglomeration for they stated that 'Linkage ... is ... a derived, not an original advantage; it is a method of utilising and increasing the advantage of an already developed area'. It seems inconsistent, however, to regard a sale, for example, between one West Midlands establishment and another as a 'linkage' and not a similar contact between the West Midlands and London. D. E. Keeble,s in his study of local linkage and manufac

The diffraction loss and beam size of the TEM00 mode in gas lasers have been determined experimentally. The results are in agreement with theoretically predicted values to within the experimental error, except that the increase in beam size with reduction of mirror size was found to be less than predicted.

Infrared spectra (500–195 cm.–1) in di-isopropyl ether show bands due to the complex acids, HMX4, formed on solvent extraction of Ga3+, In3+, and Tl3+ from HCl and HBr solutions, confirming previous Raman deductions. The tetrahalogeno-ions have Td symmetry with the v3 frequencies: GaCl4–= 374; GaBr4–= 274; InCl4–= 333; InBr4–= 233; TlCl4–= 293; TlBr4–= 197 cm.–1. The same frequencies are found in crystalline tetramethylammonium salts of the bromo-ions and GaCl4– but the indium and thallium chloride complex salts have different spectra attributed to pentachloro-ions.