Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: High-spin spectroscopy and shell-model interpretation of the N < 126
  radium isotopes $^{212}$Ra and $^{213}$Ra   The level structures of $^{212}$Ra and $^{213}$Ra have been established via
time-correlated $\gamma$-ray spectroscopy following the
$^{204}$Pb($^{12}$C,4$n$)$^{212}$Ra and $^{204}$Pb($^{13}$C,4$n$)$^{213}$Ra
reactions. In $^{212}$Ra, levels up to $\sim 6.2$ MeV were identified and firm
spin-parity assignments were achieved to a $J^{\pi} = 19^+$ isomer with a mean
life of 31(3) ns. For $^{213}$Ra the corresponding values were $\sim 4.5$ MeV
in excitation energy and $J^{\pi} = 33/2^+$. Two isomeric states with $J^\pi =
23/2^+$, $\tau = 27(3)$ ns and $J^\pi = 33/2^+$, $\tau = 50(3)$ ns were
discovered in $^{213}$Ra. The experimental data were compared with
semiempirical shell-model calculations, which allowed dominant configurations
to be assigned to most of the observed levels.

24
The categories of this paper are: dg-ga
17
The categories of this paper are: q-fin
5
The categories of this paper are: gr-qc
2
The categories of this paper are: math
3
The categories of this paper are: physics
20
The categories of this paper are: acc-phys
7
The categories of this paper are: hep-th
12
The categories of this paper are: nucl-th
23
The categories of this paper are: solv-int
19
The categories of this paper are: eess
35
The categories of this paper are: mtrl-th
25
The categories of this paper are: patt-sol
4
The categories of this paper are: cond-mat
11
The categories of this paper are: hep-lat
32
The categories of this paper are: atom-ph
18
The categories of this paper are: econ