Abstract
Although hydrogen molecule is known to be stable and its dissociation energy in its ground electronic (X \(^{1}\Sigma _{g}^{+}\) ) state and other bonding characteristics have been predicted correctly by ab initio quantum chemical calculations, the possibility of its formation in its lowest triplet electronic state (b \(^{3}\Sigma _{u}^{+}\) ) remains an open question. We have computed the potential energy curve for \(\hbox {H}_{2}\) in its lowest energy triplet electronic state using full configuration-interaction level calculations (within the Born–Oppenheimer approximation) using different basis sets, particularly using bond functions, and including (empirical) relativistic corrections. The potential energy minimum for the lowest triplet electronic state is shown to occur around 7.8 Bohr with a well depth ( \(D_\text {e}\) ) of 4.7 \(\hbox {cm}^{-1}\) . It is pointed out that it could support at least one bound state with a dissociation energy ( \(D_\text {0}\) ) of 0.012 \(\hbox {cm}^{-1}\) for T \(_{2}\) . It is also shown that the para form of \(\hbox {H}_{2}\) \((^{3}\Sigma _{u}^{+})\) in its lowest energy rotational state (j = 1) can support a quasi-bound state with a lifetime of at least 5 ps.
Graphical abstract
Full configuration interaction level calculations using relativistic basis functions reveal a potential energy minimum of 4.7 \(\hbox {cm}^{-1}\) for the lowest energy triplet electronic state of \(\text {H}_{2}\) that could support a vibrational bound state for \(\text {T}_{2}\) (j = 0) and \(\text {H}_{2}\) (j = 1).
