### Writing Gamma Decay (Emission) Equations

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:

---> ${\text{}}_{43}^{99}\text{Tc}$ + γ

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

---> ${\text{}}_{43}^{99}\text{Tc}$ + 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.

${\text{}}_{38}^{87}\text{Sr*}$ ---> ${\text{}}_{38}^{87}\text{Sr}$ + 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.

--->  +  ${\text{}}_{0}^{0}$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:

---> ${\text{}}_{27}^{58}\text{Co}$ + γ (0.025 MeV)

---> ${\text{}}_{27}^{58}\text{Co}$ + 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.