this has the value 8xl0" 13 . Clearly a compensating shift would occur for absorption provided source and absorber were identical and at the same temperature. A small difference in temperature between source and absorber leads to a relative shift per degree given by 6E/E =Cp/2c 2 where Cp is the specific heat. For Fe at 300°K this is 2.2xlO" 15 /°K. This is sufficient for it to be necessary to take it into account in accurate experiments using the resonance absorption of Mach's principle states that the inertial mass of a body is determined by the total distribution of matter in the universe; if the matter distribution is not isotropic, it is conceivable that the mass of a body depends on its direction of acceleration and is a tensor rather than a scalar quantity. Thus the matter in our galaxy is not distributed isotropically with respect to the earth, and hence the mass of a body on the earth may depend on the direction of its acceleration with respect to the direction towards the center of our galaxy. Cocconi and Salpeter 1 have proposed that the total inertial mass of a body on the earth be considered the sum of an isotropic part m and an anisotropic part Am, and that the contribution to the mass of a body on the earth due to a mass 9TC a distance r away from the body is proportional to < M/r p (0 ^ v ^ 1). The ratio of Am, due to a mass sn a distance r away, to m, due to the total mass in the universe, isin which p = average density of matter in the universe (10" 29 g/cm 3 ) and R = radius of the universe (3xl0 27 cm). 2 If Am is ascribed to our own galaxy, thenr = 2.5xl0 22 cm and 3Tl=3xl0 44 g, where the total mass of the galaxy is considered concentrated at its center. Hence for v-1, Am/m=2xl0" 5 and for ^ = 0, Am/m=3xl0" 10 . Cocconi and Salpeter have suggested several experiments to test for this anisotropy of mass based on the observation that the contribution to the binding energy of a particle in a Coulomb y rays, such as those to measure the gravitational red shift. 2 ' 3 I would like to thank Dr. Ziman, Professor O. R. Frisch, and Dr. W. Marshall for helpful discussions. 1 R. L. Mossbauer, Z. Physik 151, 124(1958). 2 R. V. Pound and G. A. Rebka, Phys. Rev. Letters 3, 554 (1959). 3 T. E. Cranshaw, J. P. Schiffer, and A. B. Whitehead, Phys*. Rev. Letters 4, 163(1960).potential due to the anisotropic mass term Am is AE = (Am/m)TP 2 (cos0).(2)Here T is the average kinetic energy of the particle, P 2 is the Legendre polynomial of order 2, and 9 is the angle between the direction of acceleration of the particle (determined by the direction of an external magnetic field H and by the magnetic quantum state) and the direction to the galactic center. This equation is based on the assumption that Am varies as P 2 (cos0). The first experiment suggested was to observe the Zeeman splitting in an atom 1 and the second was to observe the Zeeman splitting in the excited nuclear state of Fe 57 by use of the Mossbauer effect. 3 [The change in binding energy due to Am will not be given exactly by Eq.(2) in the nuclear ...

No abstract

they occupy a single site with trigonal anti-prism symmetry, despite the CaAl 2 O 4 fact that there are two other sites associated with octahedral symmetry.

No abstract

In this paper we calculate the potential energy surface of He3 within the SCF—LCAO—MO approximation to test the pairwise additivity of intermolecular forces at short range. We obtain large nonadditive contributions at very close distances, but in general, in the neighborhood of the van der Waals well (∼5.6 a.u.), they are negligible. However the study of a few He4 configurations shows that four-body effects can be important enough to question the convergence of many-body expansions.