The particle instability of ¹⁸B was established with the failure to observe ¹⁸B nuclei in the fragmentation products of 44 MeV/nucleon ⁴⁰Ar ions on a Ta target (1985La03,1986Po13), or in the fragmentation products of 12 MeV/nucleon ⁵⁶Fe ions on a Be target (1984Mu27). Its neutron separation energy is well known as S(n)<10 keV, hence the uncertainty in its mass excess (ΔM= 51850 keV 170) is mainly determined by uncertainty in the ¹⁷B mass (ΔM=43770 keV 170) (2012Wa38).

Theoretical Predictions:

The s-wave neutron emission, observed in (2010Sp02), is consistent with a Jπ=2- spin assignment for ¹⁸B. The shell model calculations of (1992Wa22) predict Jπ=2- for the ground state with the first three excited states at 0.45, 0.52, 0.839 MeV with Jπ=4-, 2-, 3-; an update of this calculation is given in (2010Sp02). On the other hand, (1985Po10) predicted the ¹⁸B ground state to have Jπ=4- and to have excited states at 0.62, 0.86, and 1.59 MeV with Jπ=1-, 2- and 2- (1985Po10). As discussed in (2010Sp02), the inability to definitively identify the ¹⁸B and ¹⁷B states participating in the observed decay leaves some uncertainty in the Jπ assignment.

See other general predictions in (1997Ba54,2004La24,2006Ko02,2012Yu07)