A Graphical Method for Calculating Intensities of Space-Focused Atomic and Molecular Beams

Abstract

A simple graphical method for calculating focused beam intensities in an atomic or a molecular beam resonance apparatus using space focusing is described. The method takes into account the finite sizes of the source and detector and the distribution of velocities in the beam. It can be used to determine the effect of stops and other obstacles placed in the beam. In addition to serving as a calculational tool, the method provides physical insight into the focusing process. Using the method, the dependence of focused beam intensity on the length of the C field is investigated for a symmetric apparatus. It is found that as the C field is lengthened, the focused beam intensity first increases, then slowly decreases. The results of numerical calculations are presented for a molecular beam apparatus using quadrupole A and B fields, and a beam of carbon monoxide molecules. The implications for high resolution atomic and molecular beam spectroscopy are discussed.