Studies on the proton dynamics and melting of ice crystals

本研究建立了一种新的荧光方法，可用于冰晶中质子动力学的研究。2-选择萘酚分子作为荧光探针，用皮秒脉冲激光激发。获得了以下结果。(1)用激发态质子转移模型解释了脉冲激发后荧光的衰减曲线。(2)在120 K附近，荧光寿命从5 ns逐步减小到2 ns，这与120 K以上质子在冰中迁移率的增加相一致，都是由于L缺陷迁移率的增加. (3)在72 K左右观察到寿命缩短以及快分量和慢分量之间的强度比增加。该温度被确定为质子有序转变，这仅在介电和量热测量中在KOH-dopedice中观察到。实验结果表明，我们的荧光法具有较高的灵敏度， ...更多信息 探测探针萘酚分子附近质子有序化的局部趋势的灵敏度由于跃迁附近的涨落增加使得探针分子的激发态不太稳定，并且使得寿命短。我们的结论是，包括探针分子将局部打破所谓的冰规则，并刺激质子有序没有KOH掺杂前夕。(4)为了了解萘酚分子如何包含在冰晶中，我们通过真空升华法生长了纯萘酚晶体。通过对萘酚掺杂的冰的荧光光谱的比较，对荧光光谱中的振动结构进行了归属。结果表明，存在一个与夹杂物类型有关的特征零声子位移，这将有助于进一步研究冰的熔化转变.这些结果已部分发表在几种期刊上，并在1996年8月于新罕布什尔州召开的冰的物理和化学国际会议上作了介绍.（该论文将很快发表在《物理化学杂志》上。）少

In this study, we have established a new fluorescence method which can be used for the study of proton dynamics in ice crystals. 2-naphthol molecule was chosen ad the fluorescence probe to be excited by a pico-second pulse laser. The following results were obtained.(1) The decay curves of the fluorescence after the pulsed excitation were well explained by the ESPT (excited state proton transfer) model.(2) A stepwise decrease in the flurescence lifetime from 5ns to 2ns was observed near 120K,which is consistent with the increase in the mobility of the proton in ice above 120K.They were both attributable to the L-defect mobility increase.(3) The lifetime shortening as well as the increase of the intensity ratio between the fast and slow components were observed around 72K.This temperature is identified as the proton ordering transition, which have been observed only in KOH-dopedice in dielectric and calorimetric measurements. The precent result shows that our fluorescence mothod has high … More sensitivity to detect the local tendency of proton ordering near the probe naphthol moleculesince the fluctuation increase near the transition makes the excited state of the probe molecule less stable and makes the lifetime short. We conclude that the inclusion of the probe molecule would locally break the so-called ice rule and stimulate the proton ordering eve without KOH-doping.(4) In order to see how the naphthol molecule is included in ice crystal, we grew a pure naphthol crystal by a vacuum sublimation method. From the comparison of the naphthol-doped ice spectra, we have assigned the vibrational structure in the fluorescence spectra. The result shows that there is a characteristic zero phonon shift depending on the type of inclusion, which will be useful for the continuing study on the melting transition of ice.These results were partly published in several journals and also presented in the International Meeting on the Physics an Chemistry of Ice held in New Hampshire in Aug.1996. (Proc.will be soon published in J.Phys.Chem.) Less