Decay scheme of sodium-24 Sodium-24 decays into an excited nucleus of magnesium-24. Magnesium reaches nuclear ground level via two consecutive gamma emissions. What are the half-lives (time scales) for these two processes? I think that those gamma photons are emitted very rapidly after Mg-24 is formed. I'm curious to know but I cannot find data. I'm a Chem undergrad with interests in nuclear chemistry.
For energy levels in nuclei (and their gamma emission) the first place to look is at the Evaluated Nuclear Structure Data Files. I usually use the Brookhaven site, but there may be a closer mirror to you. Enter 24 into the Nuclide or Mass box and hit Enter. Check the 'Adopted Levels, Gamma' box by $^{24}$Mg, and request the pdf version (back up at the top).
On the last page you will find the lower levels like this (although rotated by 90 degrees):

So, the 4122.889 keV level has a decay time of 22 fs - this is the level that the first gamma decays from. The 1368.672 keV level has a decay time of 1.33 ps - this is the second gamma in your sequence.