Section A - Radiocarbon dating Flashcards
what are the naturally occuring isotopes of Carbon?
Naturally Occurring Isotopes of Carbon
12^C 98.89%
13^C 1.11%,
14^C 0.00000000010% (1 in 10^12)
what is radiocarbon dating?
Cosmic ray generated neutrons interact with 14^N in the atmosphere, providing a roughly constant amount of 14^C
Neutrons from thermonuclear reactions (including nuclear power plants) interacting with 14^N.
what is a scintillator detector?
These are effective as measuring gamma radiation
The scintillator material emits light that is collected in photomultiplier tubes.
what is the unit of radioactivity?
In the International System of units (SI), the becquerel (Bq) is the unit of radioactivity.
how many becquerels are there in a curie?
One curie is 37 billion Bq
what is a curie?
A curie (Ci) is a unit of activity equal to 3.7 x 1010 disintegrations per second.
what are the common prefixs used with becquerels since a bq represents such a small amount?
Since the Bq represents such a small amount, you are likely to see a prefix used with Bq, as shown below:
1 MBq (27 microcuries), 1 GBq (27 millicuries), 37 GBq (1 curie), 1 TBq (27 curies).
how do we detect radiation with technology?
- Ionisation (Geiger) counter
- Scintillation counter
- Accelerator Mass Spectrometry (AMS)
what is accelerator mass spectrometry?
AMS is ultrasensitive isotope ratio mass spectrometry of small prepared samples.
what is the difference between Accelerator mass spectrometry and radiation counters?
AMS counts the number of atoms in the sample, while scintillation counters measure the infrequent radioactive decay events in the sample.
what is the duration difference between accelerator mass spectrometry and radiation counters?
10mg C contains 6x108 atoms 14C and AMS would give 1000 counts in 0.1 sec while a scintillation count would take 5 days.
how do you calculate activity?
activity = rate of decay = k x N
Activity is proportional to the number of nuclei.
