The $O_u^{+}$${(}^3$${\Pi }_u$)←${\mathrm{XO}}_g^{+}$${(}^1$${\Sigma }_{\mathit{g}}^{+}$) excitation spectrum of ${\mathrm{Zn}}_2$ van der Waals molecules produced in a molecular beam employing free-jet supersonic expansion, crossed with a pulsed dye-laser beam, was studied using Ar as the carrier gas. A well-resolved structure arising from transitions between the vibrational levels of the lower and upper states was recorded at various carrier gas pressures. An analysis of the spectrum yielded the vibrational constants, bond strengths, and equilibrium internuclear separations of the molecule in the two electronic states.

• Received 14 August 1989

DOI:https://doi.org/10.1103/PhysRevA.41.277