DETECTION AND SPECTROSCOPY OF SINGLE PENTACENE MOLECULES IN A PARA-TERPHENYL CRYSTAL BY MEANS OF FLUORESCENCE EXCITATION
DETECTION AND SPECTROSCOPY OF SINGLE PENTACENE MOLECULES IN A PARA-TERPHENYL CRYSTAL BY MEANS OF FLUORESCENCE EXCITATION
复制标题
DOI：
10.1063/1.461392
复制
发表时间：
1991-11-15
影响因子：
4.4
通讯作者：
MOERNER, WE
中科院分区：
文献类型：
--
作者：
AMBROSE, WP;BASCHE, T;MOERNER, WE
高效率荧光激发光谱的最新进展，极大地改善了对三苯晶体中并五苯单个单分子在低温（1.5 ~ 10 K）下的第一次电子跃迁的光谱。我们观察到两类单分子的行为：一类分子具有与时间无关的共振频率，而二类分子在几个共振频率之间随时间呈扩散运动，我们称之为“光谱扩散”，类比于非晶材料中常见的类似效应。报道并分析了线宽的温度依赖性和荧光发射率和线宽的功率依赖性。描述了令人惊讶的Il类行为的各种形式，包括在几个离散频率之间跳跃，以许多小步骤向非均匀线的中心爬行，以及在许多可能的共振频率之间徘徊。II类行为的发生仅限于非均匀线的翅膀，这表明这种效应与某种形式的局部紊乱有关。光谱扩散速率随温度升高而增加，表明这种效应可能是由于声子辅助的并五苯缺陷周围局部自由度的转变，其来源仍有待确定。
Recent advances in fluorescence excitation spectroscopy with high efficiency have produced greatly improved optical spectra for the first electronic transition of individual single molecules of pentacene in p-terphenyl crystals at low temperatures (1.5 to 10 K). Two classes of single molecule behavior are observed: class I molecules have time-independent resonance frequencies, and class II molecules show a diffusive motion among several resonant frequencies with time which we term "spectral diffusion" by analogy with a similar effect which is common in amorphous materials. The temperature dependence of the linewidth and the power dependence of the fluorescence emission rate and of the linewidth are reported and analyzed. Various forms of the surprising class Il behavior are described, including jumping among several discrete frequencies, creeping toward the center of the inhomogeneous line in many small steps, and a wandering among many possible resonance frequencies. The occurrence of class II behavior is restricted to the wings of the inhomogeneous line suggesting that the effect is correlated with some form of local disorder. The spectral diffusion rate increases with increasing temperature, suggesting that the effect may be due to phonon-assisted transitions of local degrees of freedom around the pentacene defect whose source remains to be identified conclusively.