Other methods

Abstract

Caesium is an element with relative atomic mass of 132.905 and atomic number 55. It is a very reactive silvery-white metal which resembles sodium and has a relative density of 1.87. Its melting point is 28.4°C and its boiling point is 678°C. The natural isotope ¹³³Cs (abundance 100%) is stable and there are 34 radioisotopes as well. Compounds are rare and the element is used in photoelectric cells and as a catalyst. The interesting isotopes are ¹³⁵Cs and ¹³⁷Cs. Both are radioactive with half-lives of 2.3 Ma and 30 a, respectively. They are produced with equal yields of c. 6 to 7% in binary fission of actinide nuclides. Caesium nuclei enter the environment through atmospheric testing of nuclear weapons and release from nuclear industry. ¹³⁷Cs is a well-known tracer and time marker whereas, according to Lee et al. (1993). ¹³⁵Cs has been practically disregarded because its long half-life precludes detection by counting, and also that in conventional mass spectrometers the tail from the stable ¹³³Cs swamps its signal (since its abundance is typically 10^-9 smaller).