EFFECTS OF PROTON MOTIONS ON THE FLUORESCENCE FROM 2-NAPHTHOL-DOPED ICE IH AND THE PROTON ORDERING TRANSITION

Fluorescence from 2-naphthol-doped ice Ih crystals was studied using a picosecond pulsed laser. Because of the incipient ESPT (excited state proton transfer) process of 2-naphthol in ice, the fluorescence lifet ime is sensitive to the change in the proton configurations around the dopant. In addition to the sharp decrease above 120 K due to the incr ease in the mobility of proton defects, the lifetime shows a dip near 72 K, which is related to the Ih-XI proton ordering transition.