LTH, Lund

The nuclear mass at finite angular momenta

in collaboration with Filip Kondev, Eddie Paul, Mark Riley and John Simpson

Experimental nuclear masses are often shown as the experimental shell energy', i.e.

E_{shell}(Z,N) = E_{exp}^{g.s.}(Z,N) - E_{ld}(Z,N)

where $E_{exp}^{g.s.}$ is the observed energy of the ground state and $E_{ld}$ is some liquid drop or droplet model expression. This definition can be generalized to define an experimental shell energy for a specific nucleus at a fixed angular momentum $I$,

E_{shell}(Z,N,I) = (E_{exp}^{g.s.}(Z,N) + E_{exc}(Z,N,I)) - E_{rld}(Z,N,I),

i.e. the total observed energy of a high spin state relative to the rotating liquid drop energy, $E_{rld}(Z,N,I)$.

The shell energy $E_{shell}(Z,N,I)$ gives a new insight into different phenomena at high spin, e.g.

It becomes possible to compare high-spin states in different mass regions and thus different ways to build angular momenta.
Odd and even nuclei have similar properties at high spin illustrating the disappearance of pairing?
For many isotopes, we observe a reversed odd-even staggering at intermediate spin values.
The question if any new magic numbers' show up at high spin can be investigated.
In some cases, spin values can be determined from interpolation (extrapolation) in $Z$, $N$ or $A$.
Calculated and observed high-spin states can be compared on an absolute scale.
The expected smooth trends at high spin can be used as a new input when estimating masses which have not been measured.

For many nuclei in which very high-spin states have been observed, the ground state mass is not known or measured with a large uncertainty. Thus, systematic mass measurements with an accuracy of $\pm 10$ keV or so are important for the present study.

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