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Mass of ²⁰O: The mass excess of ²⁰O is estimated as 13.3 ± 2 MeV by extrapolation from heavier A = 4n isobars (see (SH54D, 55AJ61)). ²⁰O is then stable to neutron emission by ~ 4 MeV.

²⁰O has not been observed. A recent attempt to detect its β-decay was unsuccessful: (KA56D) bombarded ¹⁸O with 40-MeV α-particles (¹⁸O(α, 2p)²⁰O, Q_m = -20.3) and found that τ_1/2 is not in the range 10 min to 150 years. If τ_1/2 is between 1 sec and 10 min, the cross section for the (α, 2p) reaction is less than a few milibarns.

Two possible reactions leading to ²⁰O are ¹⁸O(t, p)²⁰O (Q_m = -0.5) and ²²Ne(n, ³He)²⁰O (Q_m = -22).