Isotope-ratio mass spectrometry isotopic make up of the sample is obtained. For example, carbon isotope ratios are measured relative to the international standard for C. The C standard is produced from a fossil belemnite found in the Peedee Formation, which is a limestone formed in the Cretaceous period in South Carolina, U.S.A. The fossil is referred to as VPDB (Vienna Pee Dee Belemnite) and has C:C ratio of 0.0112372. Oxygen isotope ratios are measured relative the standard, V-SMOW (Vienna Standard Mean Ocean Water). It is critical that the sample be processed before entering the mass spectrometer so that only a single chemical species
Isotopes of fermium Isotopes of fermium Fermium (Fm) is a synthetic element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be discovered (in fallout from nuclear testing) was Fm in 1952. Fm was independently synthesized shortly after the discovery of Fm. There are 20 known radioisotopes ranging in atomic mass from Fm to Fm (Fm is unconfirmed), and 2 nuclear isomers, Fm and Fm. The longest-lived isotope is Fm with a half-life of 100.5 days, and the longest-lived isomer is Fm with a half-life of 1.8 seconds. Fm? was