Observation of bound-free photodissociation ofH3+

We have observed a bound-free photodissociation of ${\mathrm{H}}_3^{+}$ caused by a single-photon absorption from highly excited rovibrational levels of the ${\mathrm{H}}_3^{+}$ ground state into the continuum of the first-excited singlet electronic state. The apparent threshold energy of the dissociation has been measured to be ∼2.5 eV, in agreement with the calculated one by Talbi and Saxon [D. Talbi and R. Saxon, J. Chem. Phys. 89, 2235 (1988)].