Q value (nuclear science)

In nuclear physics and chemistry, the Q value for a reaction is the amount of energy absorbed or released during the nuclear reaction. The value relates to the enthalpy of a chemical reaction or the energy of radioactive decay products. It can be determined from the masses of reactants and products. Q values affect reaction rates. In general, the larger the positive Q value for the reaction, the faster the reaction proceeds, and the more likely the reaction is to "favor" the products.

${\displaystyle Q=(\,m_{\text{r}}-m_{\text{p}}\,)\times {\text{0.9315 GeV }}}$

where the masses are in atomic mass units. Also, both ${\displaystyle \;m_{\text{r}}\;}$ and ${\displaystyle \;m_{\text{p}}\;}$ are the sums of the reactant and product masses respectively.