Studies on the proton dynamics and melting of ice crystals

在这项研究中,我们建立了一个新的荧光方法可用于研究质子动力学在冰晶。选择2-萘酚分子作为荧光探针，用皮秒脉冲激光激发。得到了以下结果：(1)用激发态质子转移（ESPT）模型很好地解释了脉冲激发后荧光的衰减曲线。(2)在120K附近，荧光寿命从5ns逐渐减小到2ns，这与120K以上质子在冰中的迁移率增加是一致的。它们都归因于l缺陷迁移率的增加。(3)在72K左右，寿命缩短，快、慢组分强度比增大。这个温度被确定为质子有序跃迁，这只在电介质和量热测量中观察到。目前的结果表明，荧光方法对探测萘酚分子附近的质子有序的局部趋势具有较高的灵敏度，因为在跃迁附近波动的增加使得探测分子的激发态不稳定，寿命短。我们得出结论，探针分子的包含将局部打破所谓的冰规则，并刺激质子有序即使没有koh掺杂。(4)为了了解萘酚分子是如何包含在冰晶中的，我们用真空升华法生长了一个纯萘酚晶体。通过对掺萘酚冰光谱的比较，我们确定了荧光光谱中的振动结构。结果表明，在不同类型的包合物中存在一个特征的零声子位移，这将为进一步研究冰的融化转变提供参考。这些结果部分发表在若干期刊上，并在1996年8月在新罕布什尔州举行的冰的物理和化学国际会议上提出。（这篇论文将很快发表在j.p yphys.chem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