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Flashcards in Dating and Geographic Origin Deck (6)
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1
Q

What is alpha decay?

A

Alpha decay is where an atom loses an alpha particle.

The resulting nucleus has an atomic number less than two and a mass number that is 4 less than the original nucleus.

2
Q

What is beta decay?

A

A neutron is converted into a proton and an electron is emitted from the atom.

The product nucleus has an atomic number 1 more than the original nucleus.

3
Q

What is positron emission?

A

A proton is converted to a neutron and a positron is ejected.

The atomic number is one less than the original nucleus although the mass stays the same.

4
Q

What is electron capture?

A

The conversion of a proton to a neutron as the nucleus captures an electron from inner orbital.

Product nucleus has an atomic number one less than the original nucleus although the mass remains the same.

5
Q

How is Carbon 14 produced and how is it distributed in the environment?

A
  • Cosmic ray generated neutrons interact with 14N in the atmosphere.
  • Neutrons from thermonuclear reactions interact with the 14N.
  • 14C rapidly oxidises to 14CO and 14CO2
  • This gets mixed into the atmosphere through plant uptake and ocean exchange.
6
Q

Why is it advantageous to used AMS over radiation counters?

A

AMS counts the number of atoms in the sample, while scintillating counters measure the infrequent radiation decay events in the sample.

10mg C contains 6 x 108 atoms of 14C and AMS would give 1000 counts in 0.1 seconds while a scintillating count would take 5 days.