ABSTRACT
This chapter introduces some of the important variables in an isotope separation process and show how the beam shape influences the commercial success of the process. Multiple-photon infra-red (IR) excitation is the absorption of many IR photons by a single molecule; often these photons differ in frequency, requiring various sources to be used in the process. The excitation of the lower vibrational levels is of particular interest in isotope separation since this stage of the process determines the isotope selectivity of the multiple-photon process. Multiple-photon excitation using infrared lasers usually refers to the molecular route, and the isotope separation technique based on this is called Molecular Laser Isotope Separation (MLIS). The multiple wavelengths required for most isotope separation processes can now be shaped with the same element with small perturbations in the size and location of the shaped light, but not in the intensity profile.
