Double-minimum potential-energy curve resulting from the adiabatic effect: The hΣg+3state ofH2

Calculations of the adiabatic effects for the ${\mathrm{h}}^3$ ${\mathrm{\Sigma }}_{\mathrm{g}}^{+}$ state of the hydrogen molecule have been performed using an explicitly correlated wave function. It is shown that in contrast to the Born-Oppenheimer results the adiabatic potential-energy curve for the h state is characterized by a double-minimum function. The nature and consequences of this finding are discussed.