Radiation sources, historical development

Reference materials for radioisotopes have mainly been used for purposes relating to nuclear and radiation safety. Historically, the development of such materials first arose from the need to assess the risk to human populations caused by worldwide contamination of food and the environment as a consequence of atomic bomb testing - particularly from bombs exploded in the atmosphere. Even now, although atmospheric testing ceased many years ago, the residues from these tests still remain the main source of radionuclides such as Cs and °Sr in the global environment (though locally, other sources may be more important in some countries). 

Photoelectron spectroscopy (PES) is a technique based on the photoelectric effect, which was first documented in 1887 by Hertz and explained in 1905 by Einstein. The use of soft x-ray sources led to the development of x-ray photoelectron spectroscopy (XPS), originally known as electron spectroscopy for chemical analysis (ESCA) [1], indicating the applicability of the method to studies of chemical properties. In parallel with the development of XPS, ultraviolet photoelectron spectroscopy (UPS) [2], i.e., PES based on ultraviolet photon sources, emerged as a tool for studying the valence electronic structure of gaseous and solid samples. However, the increasing use of the continuous spectral distribution of synchrotron radiation [3,4] as a photon source has made the historical terminology less... 

The development of chemistry has depended strongly upon careful measurements. Historically, measurements of the quantities of substances reacting and produced in chemical reactions have allowed the explanation of the fundamental nature of chemistry. Exact measurements continue to be of the utmost importance in chemistry, and are facilitated by increasingly more sophisticated instrumentation. For example, atmospheric chemists can determine a small degree of stratospheric ozone depletion by measuring minute amounts of ultraviolet radiation absorbed by ozone with satellite-mounted instruments. Determinations of a part per trillion or less of a toxic substance in water may serve to trace the source of a hazardous pollutant. This section discusses the basic measurements commonly made in chemistry and environmental chemistry. 

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