Particle-core coupling in ${}^{37}\mathrm{S}$

Excited states of the neutron-rich $N=21 {}^{37}\mathrm{S}$ nucleus have been studied using binary grazing reactions produced by the interaction of a 215-MeV beam of ${}^{36}\mathrm{S}$ ions with a thin ${}^{208}\mathrm{Pb}$ target. The magnetic spectrometer, PRISMA, and the $\gamma$-ray array, CLARA, were used in the measurements. The level scheme of ${}^{37}\mathrm{S}$ was established to an excitation energy of 4196 keV and a number of new transitions were observed, in particular that corresponding to the decay of the proposed $J^{\pi }=(11/2{}^{-})$ level at an excitation energy of 2776 keV. The structure of the state is discussed within the context of state-of-the-art shell-model calculations using the SDPF-U effective interaction; the main component of the wave function corresponds to the coupling of the odd $1f_{7/2}$ neutron to the first $2^{+}$ state of the ${}^{36}\mathrm{S}$ core. The electromagnetic decay properties of the state are discussed within the context of a particle-core coupling model and the shell model. The other members of the multiplet of states are also discussed.

Figure 1

Yields of ions detected at the PRISMA focal-plane detectors as a function of $N/Z$ for atomic numbers in the range from 12 to 20. The $N/Z$ values of projectile and target are indicated.

Figure 2

Mass spectrum for sulfur ($Z=16$) isotopes populated in the present work. See text for details.

Figure 3

One-dimensional Doppler-corrected $\gamma$-ray energy spectrum observed in association with ${}^{37}\mathrm{S}$ nuclei detected at the focal plane of the PRISMA spectrometer. See text for details.

Figure 4

One-dimensional Doppler-corrected $\gamma$-ray energy spectrum corresponding to target-like fragments observed in association with ${}^{37}\mathrm{S}$ nuclei detected at the focal plane of the PRISMA spectrometer. Photopeaks marked with “Pb-X” correspond to characteristic lead x rays from the lead target. The most intense photopeaks correspond to $\gamma$-ray transitions de-exciting the known neutron hole states of ${}^{207}\mathrm{Pb}$.

Figure 5

A comparison of the level schemes from the ${}^{36}\mathrm{S}$(n, $\gamma$)${}^{37}\mathrm{S}$ thermal neutron capture study [18], the ${}^{37}\mathrm{Cl}(t,{}^3\mathrm{He}){}^{37}\mathrm{S}$ reaction [17], the ${}^{36}\mathrm{S}$(d, p)${}^{37}\mathrm{S}$ nucleon-transfer study of Thorn et al. [19], and the proposed level scheme from the present work. The states identified by Thorn et al. are shown with energies and $J^{\pi }$ values taken from the evaluation of Cameron et al. [21]. The results of $sd\text{−}pf 0\hslash \omega$ shell-model calculations are also included. $J^{\pi }$ values of the levels based on the present work, where previously established, have been taken from the evaluation of Cameron et al. [21]. Other proposed spins and parities are based on the present work. Energies are in units of keV. See text for details.

Figure 6

Percentage of the wave function of the $J^{\pi }=3/2^{-},5/2^{-},7/2^{-},9/2^{-}$, and $11/2^{-}$ states of ${}^{37}\mathrm{S}$ which corresponds to the coupling of the odd $1f_{7/2}$ neutron to the first $2^{+}$ state of the ${}^{36}\mathrm{S}$ core. The excitation energies of the states (excluding the $J^{\pi }=7/2^{-}$ state) with the largest such component in the wave function are shown, together with the proposed experimental counterparts. See text for details.