Study of the UV two-photon ionization of aromatic solutes in liquid methylcyclohexane by the subnanosecond photostimulated ion pair dissociation technique

The photoionization of anthracene and tetramethyl-p-phenylenediamine in liquid methylcyclohexane is studied by the measurements of the de photoconductivity of — 1880 — solutions together with a new laser kinetic technique. It is based on the measurements of the photocurrent enhancement caused by the additional photoexcitation of geminate electrons. The electrons were produced by two photon ionization of the solutes using the picosecond UV laser pulse at 360 or 270 nm and then they were excited by the IR pulse at 1080 nm. For the Gaussian, exp(-r2/G2), and exponential, r-2exp(-r/B), forms of the initial distribution of separation distances between electrons and their parent cations the G and B parameters were found from the experimental dependence of the ER enhanced photocurrent on the interpulse delay in the subnanosecond domain. It is concluded that the distances obtained by the kinetic measurements can be consistent with activation energies of a free carrier quantum yield when it is considered that the autoionization of highly excited states of the aromatic solutes, initially produced by the UV laser excitation, is more prompt than their relaxation