Mass of ¹⁶Ne

Abstract

The mass of ¹⁶Ne has been measured by the reaction ²⁰Ne(⁴He, ⁸He) ¹⁶Ne at a beam energy of 129 MeV. The target gas of isotopically enriched ²⁰Ne (>99.5% ²⁰Ne) was contained in a gas cell with Havar windows. Reaction products were detected at the focal plane of an Enge split-pole spectrograph by a single-wire gas proportional counter backed by a Si surface barrier detector. Particle identification was determined from 1) energy loss in the gas, 2) total energy and 3) time of flight relative to the cyclotron RF. The reaction was observed at a lab angle of 7.5°. A total of 25 events were obtained at an approximate reaction cross section of 1 nb/sr. The mass excess of ¹⁶Ne was found to be 23.984 ± 0.024 MeV. The value is in good agreement with the quadratic isobaric multiplet mass equation although small cubic and quartic coefficients are found for the A=16 isobaric quintet for the fit to the four-parameter IMME.