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I used to think that all nuclei have fixed intrinsic value of the nuclear spin quantum number, $I$. For example, $\ce{^1H}$ must have a nuclear spin of $\frac{1}{2}$, $\ce{^{14}N}$ must have a nuclear spin of 1 and so on.

Not until I study Mossbauer spectroscopy, in which the transition involved is the excitation from $I = \frac{1}{2}$ to $I = \frac{3}{2}$ of $\ce{^{57}Fe}$ nuclei. It is the $I$ that got changed, not the $m_I$ as in typical NMR!

enter image description here

Source: Wikipedia, Mossbauer Spectroscopy

How can the $I$ of a nuclear species be changed? It was just as weird as changing the mass of a particle, which is an intrinsic property. Any insight will be appreciated.

Since the spin of nuclei can be changed, is it also possible to change the spin, $s = \frac{1}{2}$ of an electron, if given high enough energy?

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    $\begingroup$ "is it also possible to change the spin, s = 1/2?" No. Just no. $\endgroup$ Feb 1, 2022 at 20:38
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    $\begingroup$ Just a small note about formatting; please use $\ce{^57Fe}$ $\ce{^57Fe}$ instead of $^{57}$Fe $^{57}$Fe. The latter looks correct, but the alignment of superscripts might not be entirely correct (depending on e.g. fonts), and (more importantly) if you resize your window the Fe may be shifted to the next line (see example here). Using MathJax to typeset the entire nuclide symbol avoids this issue, and is probably a bit easier to keep track of mentally anyway. $\endgroup$ Feb 1, 2022 at 21:36
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    $\begingroup$ @Thelearner An alternative, plain text notation is iron-57. $\endgroup$
    – Poutnik
    Feb 2, 2022 at 11:21

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The major mistake is considering a nucleus like if it were an elementary particle.

Compare a nucleus spin configuration to spin electronic configuration of atoms. In both cases, there are multiple fermions (nucleons or electrons) that can have various total spín configuration.

There are multiple known isotopes with known excited high spin nuclear isomers.

My favourite isotopes of tantalum show that some isotopes have up to 7 isomers like tantalum-179, with spin 7/2, 9/2, 1/2, 21/2, 23/2, 25/2 and 37/2.

One of known meta-stable nuclear isomers is even naturally occuring and observationally stable (due forbidden transition): tantalum-180m, even if the lower energy tantalum-180 is unstable and has the half-life about 8 hours, beta decaying to hafnium-180 (EC, 86%) or tungsten-180($\beta -$, 14%).

Military circles have been interested for some time in the metastable isomer hafnium-178m2 with the half-life 31 years. The supposed stimulated gamma emission would provide about 1/100 energy density, compared to nuclear fission, while bypassing nuclear weapon regulations, as seen in hafnium controversy.

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  • $\begingroup$ Is there a story as to why tantalum is your favourite? :-) $\endgroup$ Feb 1, 2022 at 21:33
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    $\begingroup$ @orthocresol No special story :-), I have just mentioned $\ce{^{180\mathrm{m}}Ta}$ several times recently on CH SE, in various context. It is the only stable odd-odd nuclide after 14N, kinetically protected by its high spin configuration. $\endgroup$
    – Poutnik
    Feb 1, 2022 at 21:48
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    $\begingroup$ Tantalum-180m is also the only metastable nucleus known to occur in nature. $\endgroup$ Feb 1, 2022 at 22:10
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    $\begingroup$ While the stable one is unstable. // See also hafnium controversy about hafnium-180m2. $\endgroup$
    – Poutnik
    Feb 1, 2022 at 22:12
  • $\begingroup$ oops. hafnium-178m2 $\endgroup$
    – Poutnik
    Feb 1, 2022 at 22:18

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