Radiation, theory

Lindemann F A 1922 Discussion on the radiation theory of chemical reactions Trans. Faraday Soo. 17 598-9... 

Perrin J 1922 On the radiation theory of chemical action Trans. Faraday Soc. 17 546-72... 

Lewis s "decision" between rival theories was published in the paper written with Joseph E. Mayer, "A Disproof of the Radiation Theory of Chemical Activation," Proc.NAS 13 (1927) 623625. A copy of the news release is in the College of Chemistry Papers, 19231936, BL.UCB. Lewis wrote A. F. Joffe in fall 1927 of Mayer s failure to find a chemical reaction when a molecular stream is passed through a radiation field. Letter from G. N. Lewis to A. F. Joffe, 27 October 1927, Lewis Papers, BL.UCL. 

In addition, Perrin tended to interest himself in individual atomic events rather than in the molecule as a complex entity. The radiation theory of chemical activation attempted a mathematical representation in simple and general formulas, based on axiomatic principles. Perrin s work in radiation bears more resemblance to his reformulation of thermodynamics in the early 1900s than to his experimental work on x-rays and cathode rays in the 1890s or on colloids and Brownian motion in the early 1900s. What binds all his work together is interest in single events or the individual corpuscle. 106... 

Still, Perrin s commitment ran deep, and when he edited Job s lecture, "Mecanismes chimiques," for publication in a collection of essays after his death in 1928, Perrin added references to his own revisions of the radiation theory published in 1926 and 1928. He also appended a reprint of his 1928 article from the Comptes Rendus of the Academy of Sciences. See Formes chimiques, 154, n. 2 156, n. 2 and 160164. 

A third approach within the newly defined physical chemistry was to prove crucial to dealing with the old problems of affinity and reaction mechanisms. Like thermodynamics and radiation theory, it promised and eventually delivered a conceptual framework that constituted a truly theoretical chemistry. At the same time, this new ionic and electronic approach to chemical explanation served as an important testing ground for theoretical physicists primarily concerned with the physics tradition of ether- and electrodynamics. Helmholtz,... 

Lewis, Gilbert N., and Joseph E. Mayer. "A Disproof of the Radiation Theory of Chemical Activation." Proc.NAS 13 (1927) 623625. 

Unlike the near-field dyadic of Forster, which has no frequency dependence, the dyadics appearing in the above expression are explicitly frequency-dependent due to the range of the interaction. In particular, T p is the appropriate dyadic with the sphere in place, and fdip is the dyadic in the absence of the sphere. Although Td,p is easily obtained from dipole radiation theory, f,p must be obtained bv solvine the appropriate boundary value problem. When one considers that T( d, ra, co) - id is the electric field at the acceptor [see Eq. (8.14)], it becomes apparent that A(co) 2 is simply a ratio of intensities. For the case of transition moments which are normal to the surface as depicted in Figure 8.19, the numerator of Eq. (8.21) reduces to... 

Inc, "Atomic Radiations, Theory, Biological Hazards, Safety Measurements, Treatment of Injury, RCA, Camden, Nj(1957) 55)G.P. 

F.A. Lindemann. The Radiation Theory of Chemical Action. Trans. Faraday Soc., 17 598-606,1922. 

A related but more sophisticated concept is the random field, which occurs in radiation theory. Let u(r, t) be a field governed by some linear partial differential equation independent of time, e.g.,... 

Before leaving general theoretical considerations we must briefly examine the consequences of the simple radiation theory of unimolecular reactions. The only unimolecular reactions to which, on purely a priori grounds, it would be necessary to apply this theory would be those in which the value of the velocity constant showed no diminution whatever as the concentration was indefinitely decreased. 

E can thus be found from the Arrhenius equation in the usual way, and v calculated from it. The presence or absence pf an absorption band in the proper region is then a test of the simple radiation theory. 

Lewis and Mayer f made experiments to test whether the decomposition in the gas phase is accelerated by irradiation with the appropriate infra-red radiation. The pinene vapour was caused to stream at low pressure through a vessel intensely irradiated with infra-red radiation. The result was that none of the racemization which would have been expected on the basis of the radiation theory took place. 

Perrin s argument that the very nature of a unimolecular reaction demands independence of collisions, and therefore dependence on radiation, is adequately met both by the theory of Lindemann and by that of Christiansen and Kramers. Both these theories have the essential element in common that the distribution of energy among the molecules is not appreciably disturbed by the chemical transformation of the activated molecules thus the rate of reaction is proportional simply to the number of activated molecules and therefore to the total number of molecules, sinc in statistical equilibrium the activated molecules are a constant fraction of the whole. Thus the radiation theory is not necessary to explain the existence of reactions which are unimolecular over a wide range of pressures. 

Nevertheless the fact that nitrogen pentoxide in presence of nitrogen peroxide is decomposed by blue light, and indeed, the whole of photochemistry, shows that there is nothing impossible in principle about the radiation theory, and examples in which infra-red radiation plays some part in molecular activation may yet be discovered. 

But in addition to the considerations already mentioned there are objections of a more general kind to the radiation theory as a theory of universal applicability. 

Numerous attempts have been made to modify the original radiation theory by assuming the mechanism of activation to consist in (1) the simultaneous absorption of several quanta of different frequencies or the absorption Phys. Rev., 1924, 23, 693. 

Ithaca, NY (1963), 1H-25 CA 59, 12587-88 (1963) (The thermal radiation theory for plane flame propagation in coal dust clouds)... 

Hendrik Antoon Lorentz, from Leyden (Holland), presided the conference, whose general theme was the Theory of Radiation and the Quanta. The conference5 was opened with speeches by Lorentz and Jeans, one on Applications of the Energy Equipartition Theorem to Radiation, the other on the Kinetic Theory of Specific Heat according to Maxwell and Boltzmann. In their talks, the authors explored the possibility of reconciling radiation theory with the principles of statistical mechanics within the classical frame. Lord Rayleigh, in a letter read to the... 

Nesbet, R.K. (1971). Where semiclassical radiation theory fails, Phys. Rev. Lett. 27, 553-556. 

The processes of scattering and absorption of radiation in the atmosphere so significantly alter the spectral distribution that any similarity to extra terrestrial radiation is almost coincidental. Experiments with radiation between surfaces have shown that blackbody radiation theory can be extended successfully to many radiation heat transfer situations. In these situations the strict equilibrium requirements of the initial model have so far not proved to be necessary for practical designs. Most importantly the concept of temperature has proved useful in non-equilibrium radiation flux situations(3). 

But experiments to resolve the fine structure of the Balmer lines were difficult as you all know, resolution was impeded by the Doppler broadening of components. So ionized helium comes into the picture, because, as Sommerfeld s formula predicted, fine structure intervals are a function of (aZ)2, so in helium they are of order four times as wide as in hydrogen and one has more chance of resolving the Doppler-broadened lines. So PASCHEN [40], in 1916. undertook an extensive study of the He+ lines and in particular, 4686 A (n = 4->3). Fine structure, indeed, was found and matched against Sommerfeld s formula. The measurements were used to determine a value of a. But the structure did not really match the theory in that the quantum numbers bore no imprint of electron spin, so even the orbital properties - which dominated the intensity rules based on a correspondence with classical radiation theory - were wrongly associated with components, and the value of a derived from this first study was later abandoned. 

In the volumes to come, special attention will be devoted to the following subjects the quantum theory of closed states, particularly the electronic structure of atoms, molecules, and crystals the quantum theory of scattering states, dealing also with the theory of chemical reactions the quantum theory of time-dependent phenomena, including the problem of electron transfer and radiation theory molecular dynamics statistical mechanics and general quantum statistics condensed matter theory in general quantum biochemistry and quantum pharmacology the theory of numerical analysis and computational techniques. 

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