Measurements of proton capture in the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>A</mml:mi><mml:mo>=</mml:mo><mml:mn>100</mml:mn><mml:mtext>–</mml:mtext><mml:mn>110</mml:mn></mml:mrow></mml:math> mass region: Constraints on the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mmultiscripts><mml:mi>In</mml:mi><mml:mprescripts/><mml:none/><mml:mn>111</mml:mn></mml:mmultiscripts><mml:mo>(</mml:mo><mml:mi>γ</mml:mi><mml:mo>,</mml:mo><mml:mi>p</mml:mi><mml:mo>)</mml:mo><mml:mo>/</mml:mo><mml:mo>(</mml:mo><mml:mi>γ</mml:mi><mml:mo>,</mml:mo><mml:mi>n</mml:mi><mml:mo>)</mml:mo></mml:mrow></mml:math> branching point relevant to the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>γ</mml:mi></mml:math> process
O. Olivas-Gomez, A. Simon, Oliver C. Gorton, Jutta Escher, Emily Churchman, Patrick Millican, R. Kelmar, Craig Reingold, Adam M. Clark, N. Cooper, Craig Harris, S. L. Henderson, S. E. Kelly, F. Naqvi, A. Palmisano, D. Robertson, E. Stech, A. Spyrou, Wanpeng Tan
Abstract
The $\ensuremath{\gamma}$ process is an explosive astrophysical scenario, which is thought to be the primary source of the rare proton-rich stable $p$ nuclei. However, current $\ensuremath{\gamma}$-process models remain insufficient in describing the observed $p$-nuclei abundances, with disagreements up to two orders of magnitude. A sensitivity study has identified ${}^{111}\mathrm{In}$ as a model-sensitive $(\ensuremath{\gamma},p)/(\ensuremath{\gamma},n)$ branching point within the $\ensuremath{\gamma}$ process. Constraining the involved reaction rates may have a significant impact on the predicted $p$-nuclei abundances. Here we report on measurements of the cross sections for $^{102}\mathrm{Pd}(p,\ensuremath{\gamma})\phantom{\rule{0.16em}{0ex}}^{103}\mathrm{Ag},\phantom{\rule{0.28em}{0ex}}^{108}\mathrm{Cd}(p,\ensuremath{\gamma})\phantom{\rule{0.16em}{0ex}}^{109}\mathrm{In}$, and $^{110}\mathrm{Cd}(p,\ensuremath{\gamma})\phantom{\rule{0.16em}{0ex}}^{111}\mathrm{In}$ reactions for proton laboratory energies 3--8 MeV using the high efficiency total absorption spectrometer and the $\ensuremath{\gamma}$-summing technique. These measurements were used to constrain Hauser-Feshbach parameters used in talys 1.9, which constrains the $^{111}\mathrm{In}(\ensuremath{\gamma},p)\phantom{\rule{0.16em}{0ex}}^{110}\mathrm{Cd}$ and $^{111}\mathrm{In}(\ensuremath{\gamma},n)\phantom{\rule{0.16em}{0ex}}^{110}\mathrm{Ag}$ reaction rates. The newly constrained reaction rates indicate that the $^{111}\mathrm{In}\phantom{\rule{4pt}{0ex}}(\ensuremath{\gamma},p)/(\ensuremath{\gamma},n)$ branching point occurs at a temperature of $2.71\ifmmode\pm\else\textpm\fi{}0.05\phantom{\rule{0.28em}{0ex}}\mathrm{GK}$, well within the temperature range relevant to the $\ensuremath{\gamma}$ process. These findings differ significantly from previous studies and may impact the calculated abundances.