Background : The presolar grains originating in oxygen-neon novae may be identified more easily from those of other stellar sources if their sulfur isotopic ratios ( ^ { 33 } S/ ^ { 32 } S and ^ { 34 } S/ ^ { 32 } S ) are compared with the theoretical ones .
The accuracy of such a comparison depends on reliable ^ { 33 } S ( p, \gamma ) ^ { 34 } Cl and ^ { 34 } S ( p, \gamma ) ^ { 35 } Cl reaction rates at the nova temperature regime .
The latter rate has recently been computed based on experimental input , and many new excited states in ^ { 35 } Cl were discovered above the proton threshold .
As a result , the experimental ^ { 34 } S ( p, \gamma ) ^ { 35 } Cl rate was found to be less uncertain and 2 – 5 times smaller than the theoretical one .
Consequently , the simulated ^ { 34 } S/ ^ { 32 } S isotopic ratio for nova presolar grains was predicted to be smaller than that of type II supernova grains by a factor of 1.5 to 3.7 . Purpose : The present study was performed to confirm the existence of these new resonances , and to improve the remaining uncertainties in the ^ { 34 } S ( p, \gamma ) ^ { 35 } Cl reaction rate . Methods : Energies and spin-parities of the ^ { 35 } Cl excited levels were investigated via high-resolution charged-particle spectroscopy with an Enge split-pole spectrograph using the ^ { 32 } S ( \alpha,p ) ^ { 35 } Cl reaction .
Differential cross sections of the outgoing protons were measured at E _ { \alpha } = 21 MeV .
Distorted-wave Born approximation calculations were carried out to constrain the spin-parity assignments of observed levels with special attention to those significant in determination of the ^ { 34 } S ( p, \gamma ) ^ { 35 } Cl reaction rate over the nova temperature regime . Results : The existence of these newly discovered states are largely confirmed , although a few states were not observed in this study .
The spins and parities of a few ^ { 35 } Cl states were assigned tentatively for the first time . Conclusions : The present ^ { 34 } S ( p, \gamma ) ^ { 35 } Cl experimental thermonuclear reaction rate at 0.1 – 0.4 GK is consistent within 1 \sigma with the previous evaluation .
However , our rate uncertainty is larger than before due to a more realistic treatment of the uncertainties in the rate input .
In comparison with the previous rate evaluation , where the high and low rates differed by less than a factor of 2 over nova temperature regime , the ratio of the present limit rates is at most a factor of 3.5 at 0.12 GK .
At temperatures above 0.2 GK , we recommend the future work to focus on determination of the unknown properties of four excited states of ^ { 35 } Cl 6643 keV , 6761 keV , 6780 keV , and 6800 keV .