Intense laser dissociation of D₂⁺: From experiment to theory

Accurate angularly resolved photodissociation spectra are recorded using electric discharge for preparing the molecular ions, under intense (about 10¹⁴ W∕cm²), short (about 140 fs) laser pulse excitation at 748 nm wavelength. Such experiments are particularly convenient for the interpretation level of theoretical models that neglects ionization-dissociation competition. Abel transformation relates the center-of-mass dissociation probability to the laboratory frame observations. A spatial field average over the laser focus area, together with some statistics on molecular initial rovibrational states, yields to fragments kinetic and angular distributions that are directly comparable to experimental data. Due to small-angle Coulomb explosion, not explicitly taken into account by the model, the theory-versus-experiment confrontation can be quantitatively conducted only for angles exceeding π∕7. Very good agreement is obtained for spectra including both single- and two-photon processes that are enhanced at such high laser intensities. The level of accuracy which is reached advocates both for the correct arrangement of the different steps of the theory and for the basic mechanisms (namely, bond softening and vibrational trapping) that are used as interpretative tools.