Table of contents

The present state of the theory of the interactions of high-energy hadrons, photons, and leptons with nuclei is reviewed. Emphasis is placed on evidence for the quark-parton structure of hadrons in inelastic collisions with nuclei and on effects resulting from an increase in the secondary-particle formation lengths. The discussion is based on the space-time picture of strong interactions which follows from the multiperipheral nature of high-energy inelastic reactions.

The theory of the s process of nucleosynthesis has received considerable development during recent years, mainly as the result of more detailed physical and mathematical treatments and also as a result of the accumulation of new observational data on stellar evolution and the abundance of the elements in the solar system, and accumulation of experimental data on neutron-capture cross sections. The exact solution of the s process equations obtained recently by Newman (1978) is discussed. It confirms the correctness of the initial s process theory (Clayton, Fowler, Hull, and Zimmerman, 1961). At the same time for small neutron exposures the exact and initial solutions differ. The influence of branching of the s-process due to competition between β decay and neutron capture is analyzed; it is noted that at a temperature ~3·10⁸ K and a density of free neutrons 1.6·10⁷ cm⁻³ the s process theory is in good agreement with observational data on the yields of the various nuclides. Models are discussed for the pulsed neutron s process, which leads to formation of heavy elements in the interior of a star as the result of periodic flares of the helium shell and subsequent remixing of the material.

Ten years ago, the author published an article with the same title in this journal [Usp. Fiz. Nauk, 103, 87 (1971), Sov. Phys. Usp. 14, 21 (1971)]. The aim of the present paper is to consider the changes that have occurred during the last decade with regard to the problems considered in the earlier paper. Naturally, some new problems have also arisen, and they too are considered in the present paper.

A simple scheme is described for demonstrating laser generation of (λ = 570 nm) in an ethanol solution of rhodamin 6G excited by a small N₂ laser LGI-21 (P = 3kW, λ = 337 nm). The solution is placed into a cell of 4–5 mm thickness with a silver or aluminum mirror and a quartz window at the ends. Excitation is produced by a beam focused by a spherical lens through the quartz window. Radiation from the dye laser leaves the cell at a small angle in the direction opposite to the exciting beam through the same lens and this produces collimated radiation which is then aimed in the desired direction by deflecting mirrors.