[Triumf-seminars] TRIUMF Colloquium today at 14:00

[TRIUMF Seminars]

Date/Time: Thu 2014-08-14 at 14:00

Location:  Auditorium          

Speaker:   Calem Hoffman (Argonne National Laboratory)

Title:     Changes in the Single-Neutron Shell  Spacing of Light Nuclei

Abstract: The traditional magic numbers do not remain robust across all nuclei.  Described by large gaps in the underlying single-particle orbitals, the locations of the magic numbers vary throughout the chart of nuclides due to movement of the orbital energies. One of the most drastic regions for shell evolution is in the neutron p-sd orbitals (3 < N < 20). Here, single-particle energy gaps at N = 8 and 20 are reduced while there is an emergence of new shell gaps at N = 16 and Z = 14. A great deal of recent effort, both experimentally and theoretically, has been invested in an attempt to disentangle the dominant components of the nuclear force driving these new features.  In this talk, results from recent measurements on the single-particle structure of p-sd shell nuclei (A ~ 20) will be presented. Spectroscopic information, key to understanding the underlying single-particle structure including angular distributions, single-particle energy centroids, and two-body matrix elements, have been extracted from transfer reactions carried out in inverse kinematics. The HELIOS spectrometer, a leading device for these types of reactions, was used along with light-mass neutron-rich radioactive beams provided by the ATLAS in-flight facility at Argonne National Laboratory. I will discuss the impact of these results on our current understanding of shell spacing in light nuclei, including comparisons with modern shell-model calculations and the identification of a simple systematic trend which describes these nuclei surprisingly well.

Refreshments 15 minutes the talk.

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