We present experimental and theoretical studies of the absorption, emission, and photodissociation spectra of ${\mathrm{Rb}}_2$ molecules in solid helium. We have identified 11 absorption bands of ${\mathrm{Rb}}_2$. All laser-excited molecular states are quenched by the interaction with the He matrix. The quenching results in efficient population of a metastable $\left(1\right){}^3\Pi _u$ state, which emits fluorescence at $1042\mathrm{nm}$. In order to explain the fluorescence at the forbidden transition and its time dependence we propose a new molecular exciplex ${\mathrm{Rb}}_2\left({}^3\Pi _u\right){\mathrm{He}}_2$. We have also found evidence for the formation of diatomic bubble states following photodissociation of ${\mathrm{Rb}}_2$.

• Received 9 June 2006

DOI:https://doi.org/10.1103/PhysRevA.74.032504