Discovery of34g,mCl(p,γ)35Arresonances activated at classical nova temperatures
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abstract
Background: The thermonuclear $^{34g,m}$Cl($p,\gamma$)$^{35}$Ar reaction
rates are unknown due to a lack of experimental nuclear physics data.
Uncertainties in these rates translate to uncertainties in $^{34}$S production
in models of classical novae on oxygen-neon white dwarfs. $^{34}$S abundances
have the potential to aid in the classification of presolar grains.
Purpose: Determine resonance energies for the
$^{34g,m}$Cl($p,\gamma$)$^{35}$Ar reactions within the region of astrophyical
interest for classical novae to a precision of a few keV as an essential first
step toward constraining their thermonuclear reaction rates.
Method: $^{35}$Ar excited states were populated by the
$^{36}$Ar($d,t$)$^{35}$Ar reaction at $E$(d)=22~MeV and reaction products were
momentum analyzed by a high resolution quadrupole-dipole-dipole-dipole (Q3D)
magnetic spectrograph.
Results: Seventeen new $^{35}$Ar levels have been detected at a statistically
significant level in the region $E_x\approx$~5.9-6.7~MeV ($E_r$ \textless~800~
keV) and their excitation energies have been determined to typical
uncertainties of 3~keV. The uncertainties for five previously known levels have
also been reduced substantially. The measured level density was compared to
those calculated using the WBMB Hamiltonian within the $sd-pf$ model space.
Conclusions: Most of the resonances in the region of astrophyical interest
have likely been discovered and their energies have been determined, but the
resonance strengths are still unknown, and experimentally constraining the
$^{34g,m}$Cl($p,\gamma$)$^{35}$Ar reaction rates will require further
experiments.
