The radiative proton-capture reactions ${}^{19}\mathrm{Ne}$($p,\gamma$)${}^{20}\mathrm{Na}$, ${}^{23}\mathrm{Mg}$($p,\gamma$)${}^{24}\mathrm{Al}$, ${}^{27}\mathrm{Si}$($p,\gamma$)${}^{28}\mathrm{P}$, ${}^{31}\mathrm{S}$($p,\gamma$)${}^{32}\mathrm{Cl}$, and ${}^{35}\mathrm{Ar}$($p,\gamma$)${}^{36}\mathrm{K}$ potentially influence energy generation and/or nucleosynthesis during explosive hydrogen burning in classical novae and/or type I x-ray bursts. The thermonuclear rates of these reactions are dependent on resonance energies $E_r=E_x-Q$ and strengths $\omega \gamma$. The ${}^{20}\mathrm{Ne}$(${}^3\mathrm{He}$,$t$)${}^{20}\mathrm{Na}$, ${}^{24}\mathrm{Mg}$(${}^3\mathrm{He}$,$t$)${}^{24}\mathrm{Al}$, ${}^{28}\mathrm{Si}$(${}^3\mathrm{He}$,$t$)${}^{28}\mathrm{P}$, ${}^{32}\mathrm{S}$(${}^3\mathrm{He}$,$t$)${}^{32}\mathrm{Cl}$, and ${}^{36}\mathrm{Ar}$(${}^3\mathrm{He}$,$t$)${}^{36}\mathrm{K}$ reactions have been measured using a 32-MeV, ${}^3\mathrm{He}$${}^{2+}$ beam; ion-implanted carbon-foil targets developed at the University of Washington; and the Munich Q3D magnetic spectrograph. This experiment has already yielded precision mass measurements of ${}^{20}\mathrm{Na}$, ${}^{24}\mathrm{Al}$, ${}^{28}\mathrm{P}$, and ${}^{32}\mathrm{Cl}$ [C. Wrede et al., Phys. Rev. C 81, 055503 (2010)], which are used presently to constrain the corresponding ($p,\gamma$) reaction $Q$ values. The new ${}^{24}\mathrm{Al}$ and ${}^{28}\mathrm{P}$ masses resolve a discrepancy in the energy of the lowest-energy resonance in the ${}^{23}\mathrm{Mg}$($p,\gamma$)${}^{24}\mathrm{Al}$ reaction and better constrain a direct measurement of its strength. Excitation energies in ${}^{32}\mathrm{Cl}$ and ${}^{36}\mathrm{K}$ have also been measured. An important new proton-unbound level has been found at $E_x=2196.9(7)$ keV in ${}^{36}\mathrm{K}$ and the uncertainties in ${}^{36}\mathrm{K}$ excitation energies have been reduced by over an order of magnitude. Using the new data on ${}^{36}\mathrm{K}$, the $A=36$, $T=1$ triplets have been reassigned. The thermonuclear ${}^{35}\mathrm{Ar}$($p,\gamma$)${}^{36}\mathrm{K}$ reaction rate is found to be much higher than a commonly adopted rate and this could affect energy generation in type I x-ray bursts.

• Received 10 August 2010

DOI:https://doi.org/10.1103/PhysRevC.82.035805