Nitrogen-13

Nitrogen-13 Full table
General
Name, symbol	Nitrogen-13,13N
Neutrons	6
Protons	7
Nuclide data
Half-life	<10 minutes
Parent isotopes	13O (Electron capture)
Decay mode	Decay energy
Electron capture

Nitrogen-13 is a radioisotope of nitrogen used in positron emission tomography (PET). It has a half life of a little under ten minutes, so it must be made at the PET site. A cyclotron may be used for this purpose.

Nitrogen-13 is used to tag ammonia molecules for PET.

Production

H¹ + O¹⁶ → N¹³ + He⁴

The proton must be accelerated to a kinetic energy of about 5.55 Mev or a little more.

The reaction is endothermic (i.e. the mass of the products is greater than the reactants, so energy needs to be supplied which is converted to mass).This is one reason why the proton needs to carry extra energy to produce the nuclear reaction.

The energy difference is actually 5.22 MeV, but if the proton only supplied this energy the reactants would be formed with no kinetic energy. As momentum must be conserved, the true energy that needs to be supplied by the proton is given by:

K = (1 + m / M) | E |

Role in stellar fusion

The N-13 role in the CNO Cycle.

Nitrogen-13 plays a significant role in the CNO cycle, which is the dominant source of energy in stars heavier than the sun.^[1]

12 6C	+	1 1H	→	13 7N	+	γ			+	1.95 MeV
13 7N			→	13 6C	+	e+	+	ν e	+	2.22 MeV
13 6C	+	1 1H	→	14 7N	+	γ			+	7.54 MeV
14 7N	+	1 1H	→	15 8O	+	γ			+	7.35 MeV
15 8O			→	15 7N	+	e+	+	ν e	+	2.75 MeV
15 7N	+	1 1H	→	12 6C	+	4 2He			+	4.96 MeV

External links

• PET site of the University of Melbourne

References

1. ^ Phillips, A.C. (1994). The Physics of Stars. John Wiley & Sons. ISBN 0-471-94057-7. 

Lighter: Nitrogen-12	Nitrogen-13 is an isotope of Nitrogen	Heavier: Nitrogen-14
Decay product of: Oxygen-13 (electron capture)	Decay chain of Nitrogen-13	Decays to: Carbon-13 (EC)