This discovery meant that there are three naturally occurring isotopes of carbon: Whereas carbon-12 and carbon-13 are stable isotopes, carbon-14 is unstable or radioactive.

Carbon-14 is produced in the upper atmosphere when cosmic rays bombard nitrogen atoms.

The diminishing levels via decay means that the effective limit for using c14 to estimate time is about 50,000 years. Subsequent work has shown that the half-life of radiocarbon is actually 5730 ± 40 years, a difference of 3% compared to the Libby half-life.

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AMS technology has allowed us to date very small samples (such as seeds) that were previously undatable.

Since there are practical limits to the age range of the method, most samples must be younger than 50,000 years and older than 100 years.

These so-called "solid-carbon" dates were soon found to yield ages somewhat younger than expected, and there were many other technical problems associated with sample preparation and the operation of the counters.

Gas proportional counters soon replaced the solid-carbon method in all laboratories, with the samples being converted to gases such as carbon dioxide, carbon disulfide, methane, or acetylene.

Bases may be used to remove contaminating humic acids.

Some types of samples require more extensive pre-treatment than others, and these methods have evolved over the first 50 years of radiocarbon dating.

The sample must be destroyed in order to measure its c14 content.

The first measurements of radiocarbon were made in screen-walled Geiger counters with the sample prepared for measurement in a solid form.

Any organic material that is available in sufficient quantity can be prepared for radiocarbon dating.