Laser-fluence dependence of resonance-enhanced multiphoton reduction of trivalent europium

Abstract

Efficiency of the one-color two-photon reduction of trivalent europium mediated by an f–f transition is examined with a nanosecond laser tuned at 394 nm in methanol. The divalent-europium concentration is measured by absorbance at 350 nm. The laser-fluence dependence is obtained by varying both the pulse energy and the beam size, resulting in a fluence range of 102–104 mJ cm−2. An analysis is then performed considering both the two-photon reduction of trivalent europium and the one-photon backward oxidation of divalent europium. The quantum yields of the first and second processes in the reduction are (3.8 ± 0.6) × 10−3 and 0.7 ± 0.2, respectively.