Photodissociation of Triatomic Hydrogen

We report the first observation of photodissociation of ${\mathrm{H}}_3$. Predissociation of the optically prepared ${3s}^2{A}_1^{\prime }$ and ${3d}^2{E}^{\prime \prime }$ states by the ${\tilde{X}}^2{E}^{\prime }$ ground state is detected by monitoring of the production of rovibrationally excited ${\mathrm{H}}_2$ molecules and H atoms. Product excitation is found to be highly dependent on ${\mathrm{H}}_3$ electronic and nuclear configuration.