Question

²²Na has a half life of 2.6 years. It decays to ²²Ne in an excited state of 1275 keV with a half-life of 3 ps.

In the lab, we use 1275 keV gamma rays because:

a,	22Ne is chemically seperated from 22Na.
	b,	22Ne is in secular equillibrium with its parent.
	c,	22Ne is in transient equillibrium with its parent.
	d,	There is no relation between 22Na decay and gamma emission.

Answer 1

22Ne is in secular equilibrium with its parent because:

22 Na (Father) -----> 22 Ne (Daughter) + + 1275 kev

Secular equilibrium: When the parent's the half-life is very long compared to that of the daughter's half life, the decrease of parent activity is negligible over the course of the observation period.

Transient Equilibrium : when the parent's half-life is of the order of the observation time and the daughter's half-life is considerably shorter (but not negligibly shorter).

No Equilibrium : When the daughter half-life is longer than the parent half-life, there is no equilibrium established between them.