On the High Excitation 7$α$ De-exciting States in $^{28}$Si$^*$

Abstract

A direct comparison and analysis of published spectra for the 7$α$ disassembly of $^{28}$Si projectiles excited in collisions with $^{12}$C at 35 MeV/u reveals significant agreement in the derived excitation energies of high excitation energy resonances observed in two different experiments, in contrast to some earlier conclusions reported in the literature. Many of the observed resonances have excitation energies consistent with those arrived at in recent theoretical investigations explicitly predicting the excitation energies and spins of toroidal nuclei. An AI-assisted application of well-established statistical filtering techniques reveals identical structures in all spectra investigated. Some additional peaks are observed. The possibility that they correspond to other favored geometries is discussed.

Figures (4)

• Figure 1: Observed 7$\alpha$ excitation energy spectra. Energy bins of 2 MeV are employed. The total data of reference b28 (top-dashed line) and reference b26 (bottom-solid line) are depicted. Also shown is the spectrum of events obtained in the first quarter of the experimental run of reference b28 (middle-dash-dotted line). See text.
• Figure 2: Second derivative analyses of the available $^{28}$Si → 7$\alpha$ Data. Top- Comparison of derivatives for data from FAUST experiment b28 Top-Total-solid squares, first $1/4$ of data-solid circles. Bottom- Comparison of derivatives for data from FAUST b28, triangles, and NIMROD, diamonds b26. Error bars indicate uncertainties on amplitudes of negative minima. See text.
• Figure 3: Excitation energies of second derivative derived peaks for four separate time segments vs excitation energies derived from the total 7$\alpha$ spectrum. Also shown are the predicted toroidal energies b35 plotted against themselves. See text.
• Figure 4: Second derivatives 7$\alpha$, solid squares, and 8$\alpha$ (shifted), solid circles, FAUST Events b28.