2-PHOTON EXCITATION TO THE HIGH-LYING TRIPLET-STATE OF F-3(-CENTERS IN LIF CRYSTALS() COLOR)

The excitation spectrum for the anti-Stokes luminescence band with a p eak at 538 nm, which arises from the electronic transition of the sing let excited state (1)E to the ground state (1)A(1) in F-3(+) centers o f LiF crystals, is obtained for the first time using the first harmoni c radiation of a tunable Al2O3:Ti3+ laser. From the quadratic dependen ce of the luminescence intensity on the average pumping power, the lum inescence is understood to be caused by two-photon excitation from the ground state (1)A(1) to the triplet state (3)A(2). Th, peak of the tw o-photon excitation band was determined to be located at 24331 cm(-1) from the (1)A(1) ground state.