Nearly three years have passed since the publication of the original Russian edition, in which time there have appeared various papers on recent research on the transuranium elements, of which the most notable concern the production of element 105 at Dubna and Berkeley. There has also been much fresh information on elements 104 (kurchatovium) and 103 (lawrencium). Our knowledge of shell effects in the fission barrier has been extended. Hopes of finding relatively stable superheavy elements have stimulated searches for such elements in nature as well as rapid development in heavy ion acceleration. We may see some very considerable discoveries in the next few years. The new results vary in reliability, and so it is not surprising that some papers on the properties of the heaviest elements have given rise to vigorous debates, whose value lies in the way they ad vance the subject. We have not attempted to give an exhaustive survey of recent papers and have merely added brief sections to reflect what we con sider to be the most important points from these. So far, the United states and the USSR have made the most considerable contributions to the synthesis, study, and use of the transuranium elements, so it is especially welcome to us that this book, first published in our country, should now appear in the USA in an English translation.

The Mossbauer effect is not only one of the simplest and most beautiful discoveries of nuclear phYSics, it is one of those discoveries which, to the highest degre'e, tend to produce and develop new ties between nu clear physics and the other branches of physics as well as the other natural sciences and engineering. Two of our earlier papers which form the basis of this monograph were devoted to "propaganda" for the Mossbauer effect among chemists and "propaganda" for the chemical applications of the effect among nuclear physicists. The first paper, presented in January 1962 at the Scientific Colloquium of the Learned Council of the Theory of Chemical Structure, Kinetics, and Reactivity of the Di vision of Chemical Sciences of the Academy of Sci ences of the USSR, gave a general description of the Mossbauer effect and the methods by which it is observed" and enumerated a number of problems in structural chemistry, chemical kinetics, and radiation chemlstry that might well be studied by observing the Mossbauer spectra, in particular those of organotin compounds."