Lawrence LivermoreNational Laboratory
Above ground atomic bomb testing from 1954 to 1963 produced a sudden and dramatic increase in the atmospheric level of radiocarbon (14C) globally. An exponential decline in the atmospheric levels of 14C has been occurring over the past 45 years, not because of radioactive decay, but due to mixing with the biosphere. The atmospheric14C level is mirrored in the isotopic signatures of biomolecules as carbon works it way up the food chain. We use accelerator mass spectrometry (AMS) to precisely and accurately measure the elevation in 14C above pre-bomb levels and determine the age of specific molecules. The basics of AMS will be explained and several bomb-pulse applications will be described. The technique has been used to measure the average age of DNA from selected tissues in cell biology studies and determine dates of birth or death in forensic cases.