Radiocarbon dating method
So if you have very large samples – you’ve got a big hunk of wood out of an archaeological site or a big piece of charcoal or something – and you have a very limited budget, conventional dating is worth doing because you get a result and you can possibly get more results with your budget than with AMS dating.
However, in many circumstances, sample size dictates AMS.
During the industrial revolution (1850 - present) increasing amounts of fossil fuels were combusted.
Since the carbon in these fuels was ancient, it contained no radiocarbon.
The best samples are tree rings, but annually laminated sediments have also produced excellent results. Chudy, Eristavi, Pagva, Povinec, Sivo, and Togonidze. Anthropogenic 14C variations in atmospheric CO2 and wines.
Once the radiocarbon atom is produced, it rapidly combines with oxygen (OC (7 neutrons) atoms.
This bomb radiocarbon has been gradually removed from the atmosphere by by natural processes, but the "bomb spike" can be shown through the dating by means such as comparing the bottle date and radiocarbon age of wines.
The surplus "bomb" radiocarbon is just one of the effects human have had on the ratio of C.
However, atmospheric testing of nuclear weapons in the late 1950's and early 1960's greatly increased the amount of radiocarbon in the atmosphere, so the decay rate of 14 decays per minute more than doubled.
Therefore, radiocarbon dates are calculated to a "pre-bomb" age of 1950 A. Material which died after 1950 has such high amounts of radiocarbon its age is reported as "percent modern (1950)" (example 180% modern).