Na above the proton threshold*

Globular clusters are dense groups of stars that exist near the galactic plane. Understanding their history and evolution sheds light on the history and evolution of galaxies. The presently observed stars contain elements resulting from previously unknown polluting sites. Identifying those polluting sites requires improved knowledge of nuclear reaction rates. One important rate is the ²²Ne(p, ɣ) reaction.

There are several unmeasured resonances lying just above the proton threshold for this reaction, and although many studies have been already conducted, resonances at E_cm = 68 and 100 keV (8894 and 8862 keV excited states) have not yet been confirmed. These potential resonances, which are based on two tentatively observed states in the compound nucleus ²³Na, have never been observed. In fact, it is unclear if the underlying states giving rise to these resonances even exist. These resonances have a large influence on the reaction-rate uncertainty and predicted final abundances, depending on whether they are included in the final rate.

For this experiment, we performed a new high-resolution study where a magnetic spectrograph was used to search for states above the proton threshold in ²³Na via the ²³Na(p,p’)²³Na reaction, using this reaction due to its low selectivity to the structure of the excited states.

Investigation into the existence of these states in the existing data is being performed. Preliminary results will be shown that suggest the inexistence of the Ex = 8894 and 8862 keV states.