Search for $2p$ decay of the first excited state of ${}^{17}$Ne

Abstract

Two-proton decay of the ${}^{17}$Ne low-lying states populated in the ${}^1$H(${}^{18}$Ne,$d$)${}^{17}$Ne transfer reaction was studied. The two-proton width $\hat{I}{“}_{2p}$ of the ${}^{17}$Ne first excited $3/2^{-}$ state at $E^{\ast }=1.288$ MeV is of importance for the two-proton radioactivity theory and nuclear-astrophysics applications. A dedicated search for the two-proton emission of this state was performed leading to the new upper limit obtained for the width ratio $\hat{I}{“}_{2p}/\hat{I}{“}_{\hat{I}}^3<1.6(3)\times 10^{-4}$. A novel, "combined mass" method is suggested and tested capable to improve the resolution of the experiment which is a prime significance for the study of nuclear states with extremely small particle-to-gamma width ratios $\hat{I}{“}_{\mathrm{part}}/\hat{I}{“}_{\hat{I}}^3$. The condition $\hat{I}{“}_{\mathrm{part}}\ll \hat{I}{“}_{\hat{I}}^3$ is quite common for the states of astrophysical interest which makes the proposed approach promising in this field.