Nuclear Reaction Analysis and Proton‐Induced Gamma Ray Emission

Abstract

Abstract Nuclear reaction analysis (NRA) and proton‐ (particle‐) induced gamma ray emission (PIGE) are based on the interaction of energetic (from a few hundred kilo‐electron‐volt to several mega‐electron‐volt) ions with light nuclei. Every nuclear analytical technique that uses nuclear reactions has a unique feature—isotope sensitivity. Therefore, it is insensitive to matrix effects, and there is much less interference than in methods where signals from different elements overlap. In NRA the nuclear reaction produces charged particles, while in PIGE the excited nucleus emits gamma rays. Sometimes the charged particle emission and the gamma ray emission occur simultaneously. Both NRA and PIGE measure the concentration and depth distribution of elements in the surface layer (few micrometers) of the sample. Both techniques are limited by the available nuclear reactions. Generally, they can be used for only light elements, up to calcium. This is the basis for an important property of these methods: the nuclear reaction technique is one of the few analytical techniques that can quantitatively measure hydrogen profiles in solids. Since these techniques are sensitive to the nuclei in the sample, they are unable to provide information about the chemical states and bonds of the elements in the sample. For the same reason they cannot provide information about the microscopic structure of the sample. Combined with channeling, NRA or PIGE can provide information about the location of the measured element in a crystalline lattice. The sensitivity and depth resolution of these methods depend on the specific nuclear reaction. Although NRA and PIGE are quantitative, in most cases standards have to be used. These techniques require a particle accelerator capable of accelerating ions up to several mega‐electron‐volts. This limits their availability to laboratories dedicated to these methods or that have engaged in low‐energy nuclear physics in the past (i.e., they have a particle accelerator that is no longer adequate for modern nuclear physics experiments because of its low energy but is quite suitable for nuclear analytical techniques). This article concentrates on the specific aspects of these two nuclear analytical techniques.