2
$\begingroup$

Why is the half-life of 178m2 Hafnium isotope 31 years? Maybe it is somehow related to its nuclear spin (16+)?

$\endgroup$
  • 4
    $\begingroup$ I'm voting to close this question as off-topic because this shows absolutely no research effort. $\endgroup$ – heather Sep 14 '16 at 11:22
  • $\begingroup$ Given the answer below gives a reference to a Lawrence Livermore National Lab report, I don't think you will find that level of information on Wikipedia. And, searching is polluted with the 'Hafnium controversy' which is policy, not physics (mainly). $\endgroup$ – Jon Custer Sep 14 '16 at 16:14
  • $\begingroup$ @heather Fortunately M. J. Steil could answer it without any major problems. $\endgroup$ – peterh - Reinstate Monica Sep 14 '16 at 18:33
  • $\begingroup$ Isomer not Isotope. An isomer is an isotope whose nucleus is excited to a higher quantum energy state than its ground state. An isotope can have more than 1 metastable isomers. The isomer tends to stay in the metastable excited quantum state if there are multiple lower quantum steps to fall through. This is the case with said isomer. A few nucleons will always tunnel all the way down, but this is statistically low, thus the long half-life. $\endgroup$ – 0tyranny 0poverty Jan 14 '18 at 0:11
5
$\begingroup$

I know next to nothing about nuclear isomers but I found this paper: Theoretical Assessment of 178m2Hf De-Excitation. It's third section describes the physics of hafnium isomers and on page 13 the authors write:

The decay of the $16^+$ state is highly suppressed (with a 31 yr half-life) not only because a change of $K$ by at least 8 units is required, but also because the transition has to have a high multipolarity $λ$, due to large angular-momentum differences between the initial ($J= 16^+$) and energetically feasible final states.

To understand this in detail I would recommend reading the entire third section.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.