Writing Gamma Decay (Emission) Equations

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Gamma decay equations are also called gamma emission equations.

Example #1: Write the equation for the gamma decay of the metastable form of 43-Tc-99.

Solution:

   4399m Tc ---> 4399 Tc + γ

Sometimes, the energy of the gamma ray is included in the equation. As follows:

   4399m Tc ---> 4399 Tc + γ (0.143 MeV)

MeV stands for million electron-volts. You also see it as Mev and, sometimes (incorrectly), as mev. MeV is the preferred (and correct) way.


Example #2: Write the equation for the gamma decay of the metastable form of 38-Sr-87.

3887 Sr* ---> 3887 Sr + γ (0.388 MeV)

Note the presence of the asterisk. It is another way to indicate a metastable condition. The use of 'm' is preferred, but the asterisk is in wide-spread use, so you need to know what it indicates.


Example #3: Write the equation for the gamma decay of the metastable form of 53-I-125.

    53125m I --->   53125 I  +  00 γ

Notice the use of zero for the atomic number and mass number. This is an older way to show a gamma. It has fallen into wide-spread disuse, but it does show up in reference materials on an occasional basis.

This use of zeros was also used with neutrinos nd anti-neutrinos, but its usage has also fallen off almost completely.


Example #4: 27-Co-58 has two different metastable states. How might these be shown?

Solution:

     2758m1 Co ---> 2758 Co + γ (0.025 MeV)

     2758m2 Co ---> 2758 Co + γ (0.053 MeV)

The amounts of energy must be looked up.


Example #5: Write the equation for the gamma decay of 92-U-238m

Note that 'm' (for metastable) is not used. Also, note where the gamma is written. Finally, the word energy is used where, in my above examples, I placed the Greek letter gamma.


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