X-Ray Emission Analysis of High Atomic Number Elements: A New Excitation Source Using Monoenergic 477 keVγ-Rays from the 10 B( n,α ) 7m Li→ 7 Li Reaction

Abstract

A new excitation source has been developed for x-ray emission analysis of high atomic number elements. A mixture of the sample and a small amount of boron-10 is irradiated in a thermal neutron beam and the resultant x radiation is recorded using a Ge(Li) semiconductor detector and a multichannel analyzer. The boron-10 undergoes neutron capture (¹⁰B(n,α)⁷Li, σ = 3840b) producing a single excited state of lithium-7 in 92.5% of the captures. Lithium-7m decays with a half-life of about 5×10⁻¹⁴ sec emitting a monoenergic 477 keV gamma ray. These gamma rays are in excellent geometry to the sample and are sufficiently energetic to excite the K x radiation of the highest atomic number elements known. The K x-ray spectra of several elements are presented along with a discussion of sample preparation and apparatus optimization.