Separation of the isotopes of lithium and some nuclear transformations observed with them

Abstract

In studying the transformations of elements by bombarding particles, it is of great importance to examine separately the effects due to each isotope of composite elements. It is to be anticipated that the nature of the transformations will be very different for the individual isotopes, and in a study of a complex element it may prove difficult to decide with certainly which isotope is responsible for the effects under consideration. For these reasons experiments have been made to devise methods of separation of isotopes in sufficient quantity for direct observation of the nature of the transformations produced in them. With the exception of the isotopes of hydrogen, by far the most promising method for the complete separation of isotopes is by means of some form of mass spectrograph. Unfortunately the quantities separable in this way are very small. In the mass spectrographs of Aston, Bainbridge, etc., the isotope beams produced are of the order of 10 -8 ampere or less, while for lithium a beam of a microampere would deposit only a quarter of a microgram of Li 7 per hour. The probability of disintegration of lithium by protons and diplons is, however, so large that monomolecular layers suffice for an experiment and quantities of the order of a tenth of a microgram are ample. Attention was therefore directed to obtaining quantities of this order by means of a mass spectrograph designed to give large ion beams.