Atomic masses of intermediate-mass neutron-deficient nuclei with relative uncertainty down to 35-ppb via MRTOF-MS*

Intermediate mass nuclei along the N = Z line are important components of the rp-process and accurate high-precision masses are crucial data. Half-lives of the key nuclei in the rp-process are of the order of several ten milliseconds to several seconds. The multireflection time-of-flight mass spectrograph (MRTOF-MS) has an advantage in achieving precision mass measurements for short-lived nuclei, owing to its measurement time being less than 10 ms. The SHE-mass facility, consists of the gas-filled recoil ion separator GARIS-II and an MRTOF-MS, has been developed to enable mass measurements of superheavy elements produced at RIKEN. It is also applicable to mass measurements of rp-process nuclei. Precision mass measurements of ⁶³Cu, ^64-66Zn, ⁶⁵Ga, ^65-67Ge, ⁶⁷As, ^78,81Br, ⁸⁰Rb, and ⁷⁹Sr were performed with the SHE-mass facility. In this experiment, for ⁶⁵Ga, a relative precision of δm/m = 3.5x10^-8 was obtained and the mass value was in excellent agreement with the 2016 Atomic Mass Evaluation.

We will report initial efforts using the SHE-mass facility for masses of rp-process nuclei, and will discuss future plans.