This collection of articles contains a systematic outline of original experimental and theoretical research on photoproduction of neutral pions at protons and at a strongly bound system of a few nucleons, i.e., the helium nucleus. Spark chambers and their use as spectrometers for photons and electrons are described in detail. The articles of the collection include information on a novel method of determining the efficiency of recording apparatus by generating monochromatic photons. The articles de scribe original theoretical research on the optical anisotropy of nuclei. Problems encountered in experimental studies of operating the synchrotron as a storage-type accelerator of electrons and positrons receive particular attention. The results of this research work are listed, and the problems of oppositely directed electron-positron beams in the 250-MeV synchrotron are considered. The articles should be of interest to physicists, including research workers, teachers, engineers, graduate students, and students in advanced undergraduate courses. v CONTENTS Photoproduction of Neutral Pions at Nucleons and Nuclei B.B. Govorkov, S.P. Denisov, and E.V. Minarik 0 Photoproduction of 1r Mesons at Helium and at Photon Energies of 71 160-240 MeV ...

The first part of this collection sets out the results of some experimental and theoretical investigations into the optical properties of nontransition metals. The extensive future pros pects of metal optics are indicated; the use of metal optics enables a whole series of import ant electron properties of metals to be determined. Results obtained by studying intermolecular forces (the hydrogen bond and van der Waals forces) using spectroscopic methods (Raman effect and infrared absorption) are presented in the second part. A method of studying the true absorption of the drop phase of a water cloud is described. Methods of increasing the dispersion of manufactured spectral instruments and constructing various infrared spectrometers are indicated. The publication is intended for scientific workers, graduates, and students concerned with problems of metal optics, the electron properties of metals, and molecular spectroscopy. v CONTENTS OPTICAL PROPERTIES OF NONTRANSITION METALS G. P. Motulevich Introduction .••.•......• " .................•.......••. 1 Chapter I. Method of the Kinetic Equation in Metal Optics........... 5 § 1. Kinetic equation for the infrared part of the spectrum •.•..•...•....••.••.. 5 § 2. Anomalous skin effect . • . . . . . . . . . • . • . . • . . . . • . . • • • • • . . . . • . . • . . . . . . 9 § 3. Normal skin effect • • . . . . . • . . . . • • . • . . . • • • . . . . . • . . . . .. . . 11 . . • . . . . . . § 4. Weakly anomalous skin effect. . . • • • • . . . . . . . . . . . . • • . . . . • . .. • . 13 . . . . . . .

This volume contains two papers that review certain theoretical problems that have been studied in the Laboratory of Plasma Accelerators and Plasma Physics of the P. N. Lebedev Physics Institute of the Academy of Sciences of the USSR. The review of R. R. Kikvidze and A. A. Rukhadze, "Theory of oscillations and stability of a semiconductor plasma with low carrier density in a strong electric field," is devoted to a solid-state plasma. The main attention is devoted to the fact that in such a plasma electro magnetic waves are effectively generated if there is a negative current-voltage characteristic in the carrier current; this effect can compete in importance with the well-known Gunn effect. In their fundamental review paper "Nonlinear theory of the interaction of waves in a plasma," V. V. Pustovalov and V. P. SHin set forth the fundamentals of the theory of nonlinear interaction of waves in a hot rarefied plasma. Besides a systematic exposition of the pro cedure for deriving the equations that describe the nonlinear interaction of waves in an iso tropic or an anisotropic (magnetized) plasma, they study many concrete examples relating to the interaction of definite types of waves under different conditions.