Characteristics of Escape Probabilities in Single-and Two-Color Multiphoton Ionization of Anthracene in n-Alkanes

Single-and two-color multiphoton ionization of anthracene have been compared in n- alkane solvents. The simultaneous action of 10-ns laser lights at 355 (UV) and 1064 nm (IR) gave a substantially larger time-integrated photocurrent signal (thus, the escape probability of a geminate cation-electron pair based on the Onsager model) as compared with that obtained when the UV light acted alone. It is suggested that the IR light acts through the geminate cation-electron pair to give its longer thermalization distance. For a solvent with higher electron mobility, escape probabilities for both photoionization methods tended to belarger but the relative increase in the escape probability by the additional action of the IR light tended to be smaller.