Two-color photodissociation of the lithium molecule: Anomalous angular distributions of fragments at high laser intensities

Abstract

Two-step photodissociation angular distributions are calculated by a coupled-equation approach for the 1 $^{1}\mathrm{\ensuremath{\Sigma}}_{\mathit{g}}^{+}$\ensuremath{\rightarrow}1 $^{1}\mathrm{\ensuremath{\Pi}}_{\mathit{u}}$\ensuremath{\rightarrow}1 $^{1}\mathrm{\ensuremath{\Pi}}_{\mathit{g}}$ transition in $^{7}\mathrm{Li}_{2}$. The initial excitation is induced by a low-intensity visible laser in order to select the rovibrational state. The \ensuremath{\Pi}-\ensuremath{\Pi} transition is effected by an infrared laser that is varied from weak (perturbative) to intense (nonperturbative) regimes. It is shown that laser-induced orientation effects and laser-induced resonances (trapped states) considerably alter the angular distribution of the photodissociating fragments, creating anomalies in some instances at high intensities where a nonperturbative, numerical approach is essential.