Sinan Utku

The observation of heavy elements such as Ne, Mg, Al, Si in various novae ejecta, a large isotopic abundance ratio of $\sp{22}$Ne/$\sp{20}$Ne compared to solar ratios in some meteorites, the observation of approximately 3 M$\sb{\odot}$ of live $\sp{26}$Al in the galaxy, and the correlation found in some meteorites of the $\sp{26}$Mg/$\sp{24}$Mg isotopic abundance ratio to that of $\sp{27}$Al/$\sp{24}$Mg have led to the search for mechanisms able to produce such intermediate mass nuclei. Since the Hot CNO cycle is thought to operate in white dwarves undergoing cataclysmic phases, and since the Hot CNO cycle cannot produce nuclei heavier than mass 18, one possibility is that “breakout” of the Hot CNO cycle may occur under certain conditions in novae such that A $>$ 18 elements are produced and subsequently mixed into the Interstellar Medium. The rp-process is such a breakout mechanism that proceeds by a series of proton captures and $\beta\sp{+}$ decays of nuclei (beginning with $\sp$Ne) and that follows the proton drip line.
A possible leakage into the rp-process is through the reaction $\sp$F(p,$\gamma)\sp$Ne (which would be in competition with the Hot CNO reaction $\sp$F(p,$\alpha)\sp$O). The $\sp$F($\sp{3}$He,t)$\sp$Ne reaction was used to populate states in $\sp$Ne above the proton threshold, and subsequent $\alpha$-particle and proton emissions from the $\sp$Ne were measured, to indirectly determine the relevant reaction rates. The mirror reactions $\sp$O($\sp{6}$Li,t)$\sp$Ne and $\sp$O($\sp{6}$Li,$\sp{3}$He)$\sp$F were measured to help determine the properties of relevant $\sp$Ne resonances from the properties of their isospin mirrors in $\sp$F. With the information from these measurements, the $\sp$F(p,$\gamma)\sp$Ne and $\sp$F(p,$\alpha)\sp$O reaction rates were calculated. It was found that the $\sp$F(p,$\gamma)\sp$Ne reaction occurs 10$\sp{3}$ times slower than the $\sp$F(p,$\alpha$)$\sp$O reaction over the temperature range T$\sb{9}$ = 0.1-0.5, and that leakage into the rp-process via $\sp$F(p,$\gamma)\sp$Ne should thus be small at these novae temperatures.