Abstract

Lanthanide ions in solution are photo-chemically inactive by one-photon-excitation of the f’ ← f transitions in the visible band, because the f electrons are shielded by s, p, and d electrons. It has recently been found that the photoreduction can be induced by two-photon excitation with a nanosecond laser pulse.¹ In this paper, femtosecond pulse excitation has been found to improve considerably the yield of photo-reduction of Eu³⁺ to Eu²⁺ in solution. A titanium sapphire laser is widely tunable as well as capable of producing stable femtosecond pulses with a high intensity. This laser is useful for wavelength dependent and multiphoton chemistry. The efficiency more than 0.1 has been observed by ultrashort laser excitation. It was only an order of 10^–5~–6 for two-photon chemistry with a nanosecond dye laser.

© 1995 IEEE