Nuclear Data Sheets for A=24

Abstract

Evaluated spectroscopic data and level schemes from radioactive decay and nuclear reaction studies are presented for ²⁴N, ²⁴O, ²⁴F, ²⁴Ne, ²⁴Na, ²⁴Mg, ²⁴Al, and ²⁴Si. This evaluation for A=24 supersedes the earlier one by R. B. Firestone (2007Fi14).

Highlights of this evaluation are the following:

In ²⁴O, the 7.4- and 7.65-MeV groups reported in ¹H(²⁴O,p′) (2012Ts03) and ⁹Be(²⁶F,nX) (2011Ho05), respectively, are considered as separate states in this evaluation, since the former one was observed to decay by only one neutron emission to ²³O, while the latter one by two sequential neutrons to ²²O. Based on assigned configurations, the 7.4- and 7.6-MeV groups are tentatively assigned negative and positive parities, respectively. Additional study would be useful to determine if these states are same or different.

In ²⁴Na, 2014Fi01 (n,γ) proposed J^π=(0,1,2)⁻ for 4048.8 keV level based on weaker population from the capture state (J^π=1⁺,2⁺) and mentioned to reexamine the J^π=0⁺ assignment, suggested in earlier evaluations (1990En08, 2007Fi02).

This evaluation includes the first observation of E0 transition, strength ρ²(E0)=0.380 70, for the 6432 keV transition from 0⁺ state at 6432 to 0⁺ g.s. in ²⁴Mg reported in 2020Do10. Authors proposed the first-excited 0⁺ state of ²⁴Mg to be superdeformed.

In ²⁴Al, the excited level energies deduced from (³He,t) measurements reported by different research groups vary significantly and it was not clear if some of those levels were same or different. Additional measurements are needed.