ABSTRACT
THE exchange relations and the laws of motion obtained in the last chapter form the basis of the quantum dynamics of a particle. In the systematic application of these genoral principles to the particular problems of atomic physics it is necessary to adopt a standard method of representing the various scalar and vector functions which characterise atomic systems. Aceerdingly, we shall discuss in this chapter the standard representation, simplifying the analysis by a systematic use of certain " spin" operators. The results obtainedthe proper values and matrix elements of the various operators-are of fundamental importance in atomic theory. The" spin operators" are introduced to obtain a representation which is independent of the particular co-ordinate system employed. In fact, the method of this chapter is the quantum analogue of the use of vectors in classical dynamies.
