Investigation of the $^{30}$S($p,\gamma$)$^{31}$Cl reaction via Coulomb dissociation

The Stellar reaction $^{30}$S($p,\gamma$)$^{31}$Cl was studied via Coulomb dissociation. The nucleus $^{30}$S is a candidate for the waiting point, which the reaction flow temporary stops at this nuclei, in the rapid proton capture ({\em rp}) process. The $^{30}$S($p,\gamma$)$^{31}$Cl reaction decreases the amount of $^{30}$S, and thus speeds the reaction flow of the {\em rp} process up. Therefore the strength of this reaction affects the resultant abundance and energy production in the {\em rp} process. No direct measurement of the $^{30}$S($p,\gamma$)$^{31}$Cl reaction has been made so far. The aim of the present work is to determine the resonant capture reaction rate of $^{30}$S($p,\gamma$)$^{31}$Cl from the result of Coulomb dissociation of $^{31}$Cl. The experiment was performed at the RIKEN Nishina Center. The secondary beam of $^{31}$Cl at 58~MeV/nucleon was produced and separated using the RIKEN Projectile Fragment Separator (RIPS). The beam of $^{31}$Cl bombarded a $^{208}$Pb target. The momentum vectors of the breakup products, the isotopes $^{30}$S and protons, were determined using the detectors located at downstream of the target. The relative energy spectrum of $^{30}$S + $p$ system was extracted using invariant-mass method. In this presentation, we discuss the unbound state of $^{31}$Cl which is relevant to the resonant capture in the $^{30}$S($p,\gamma$)$^{31}$Cl reaction.