[Isac-journal-club] Journal club on Ni-68

Bruno Olaizola Mampaso bruno.olaizola at triumf.ca
Fri Feb 10 17:13:57 PST 2017


Next week journal club will be on the most recent results on the
"doubly-magic?" Ni-68: "Shape coexistence from lifetime and branching-ratio
measurements in 68,70Ni" by Crider et al.

The paper is attached and here is the link:


Questions for discussion:

- Their timing spectra looks very ugly, can their uncertainties be trusted?
And their lifetime values?
- With these results there is experimental proof of shape coexistence in
almost every major shell closure. Can we expect shape coexistence in every
nuclei? If it is the norm and not the exception, is it still interesting?
- Do you think Ni-68 is doubly-magic nucleus? How should we define what is
a doubly magic nucleus?
- Ni-68 is an even-even nucleus, with these experimental results, can we
conclude that its g.s. doesn't have a band (no 2+ state)?
- One of the main systematic trends when studying the nuclear chart is the
energy of the first 2+ states, does it makes sense to use it if the first
2+ state doesn't belong to the g.s. band?

I can't think of a better thing to do in a long weekend with almost no rain
than to read some complementary papers to fully grasp the importance of
Ni-68, so I have included some concepts and papers you may want to look up
(tl;dr at the end):

- Why has Ni-68 attracted so much attention? (The introduction here is a
good starting point
http://journals.aps.org/prc/pdf/10.1103/PhysRevC.82.054301 )
- Why is N=40 a magic number in the harmonic oscillator or why could Ni-68
be a doubly-magic nucleus?
- Shape coexistence (
http://journals.aps.org/rmp/abstract/10.1103/RevModPhys.83.1467 )
- Shell Evolution type II (http://journals.aps.org/prc/

TL;DR: Ni-68 has Z=28 (magic number) and N=40 (not a "standard" magic
number in shell model, but a closure in the harmonic oscillator). It shows
almost all of the characteristics of a doubly-magic nucleus (large E(2+)
and small B(E2)), so people proposed N=40 to be a magic number, at least in
this region. But none of the nearby nuclei (like Fe-66, also with N=40)
shows any sign of (semi-)magicity, so the question about the N=40 remains


Dr. Bruno Olaizola
Postdoctoral fellow
Gamma Group

4004 Wesbrook Mall
Vancouver BC, V6T 2A3
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