B.c.c.-f.c.c. allotropy, F-bands,and metallization in xenon and krypton

APW-Xα calculations of a f.c.c.-b.c.c. phase transition in Xe prior to metallization give P ? 950 kbar, contrary to the 820 kbar result of Hama and Matsui; their use of non-touching APW spheres (f.c.c.) may be the crucial difference. Hartree-Fock plus correlation calculations in Kr indicate that f-bands play no role in rare gas crystal metallization.     

Sputtering yield measurements on H. C. P. and F. C. C. cobalt V. S. chernysh

A computer code previously set up to simulate ion penetration in amorphous solids has been extended to handle with recoil phenomena. Preliminary results are compared with existing experimental data.     

19F N.M.R. and 127I N.M.R. and N.Q.R. study of the molecular motions and deformations of iodine heptafluoride in its solid phases

In solid IF₇, ¹⁹F and ¹²⁷I N.M.R. and ¹²⁷I N.Q.R. absorption line shapes, frequencies and relaxation times have been studied from the melting temperature down to 56 K. Two new solid-solid transitions have been found at 180 K and 96 K in addition to the one already known at 153 K. The two high temperature phases are shown to be plastic. The fast molecular rotations and the slow molecular diffusion are studied from ¹⁹F and ¹²⁷I relaxation times. In the ordered phases, an analysis of the ¹⁹F second moments and longitudinal relaxation times shows the existence of a fast intramolecular exchange between axial and equatorial fluorine atoms, together with a much faster reorientation about the D ₅ axis. The characteristic times of these two motions are obtained and a mechanism for the exchange process is proposed. The chemical shift values of ¹²⁷I, the temperature dependence of the N.Q.R. frequencies and of the N.Q.R. relaxation times of ¹²⁷I, as well as the dipolar energy relaxation times have been measured and are discussed.     

Photolysis and E. S. R. Studies on Triphenylphosphinecarbethoxymethylene

Although several different groups have studied the photolysis of phosphorus ylides, none have utilized e. s. r. to support the postulated decomposition mechanisms. The fundamental question which awaits a definitive answer is which bond breaks first upon photolysis. Tschesche¹ and de Silva² utilizing the ylides (1) and (2) suggested that the carbon-phosphorus double bond was initially broken while Nagao³ using (3) proposed phenyl-phosphorus bond cleavage.     

Analysis of R. P. Smith's and D. C. Parris-R. B. Mclellan's carbon diffusivity data

A phenomenological model is proposed to account for the variation of carbon diffusivityD(N₁) with composition in austenite. This model is based on Parris-McLellan's statement that the increase ofD(N₁) with carbon concentrationN ₁ is due to the increase in chemical driving force. The gradient of the carbon activity in Wagner's and in Zupp-Stevenson's interpretation is presumed to be the intrinsic driving force. The predictions of the model are compared with carbonD(N₁) values both with [1] and without [5] a chemical concentration gradient. TheD(0) values and the carbon-carbon interaction coefficients ₁ are calculated by the use of the least squares method from the experimental data. The application of Zupp-Stevenson's definition of the activity coefficient ₁ results in a better fit of the theory to the experimental data.     

Life and work of E.F.F. Chladni

Ernst Florens Friedrich Chladni, the son of the rector of the University of Wittenberg, studied law and philosophy at the Universities of Wittenberg and Leipzig, wrote a dissertation in each of these disciplines and became an experimentalist concerned with sound and vibrations. Chladni's name is associated with the Chladni figures, and this is the first real effort to experimentally investigate the nature of sound. In the lecture the publications of Chladni are presented and, cursorily, his new instruments, designed and built by the physicist. Chladni began to tour half Europe in his own coach with sufficient space for his musical instruments. He gave lectures on the physics of plate and rod vibrations and included demonstrations of the figures and his musical instruments. Chladni's work has had a profound influence on the experimental advances in acoustics, room acoustics, in the verification of theories of superposition of waves, in elasticity, vibrational modes, sound velocities in various media, and much more. The lecture presents a portrait of the scientist Chladni, the times, and his contributions to experimental acoustics which influenced research for many decades.