Ino Daisuke, Yamada Taro, Kawai Maki
Surface Chemical Laboratory, RIKEN (The Institute of Physical and Chemical Research), Wako, Saitama 351-0198, Japan.
J Chem Phys. 2008 Jul 7;129(1):014701. doi: 10.1063/1.2949549.
The electronic excitations induced with tunneling electrons into adlayers of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) on Ag(111) have been investigated by in situ fluorescence spectroscopy in scanning tunneling microscopy (STM). A minute area of the surface is excited by an electron tunneling process in STM. Fluorescence spectra strongly depend on the coverage of PTCDA on Ag(111). The adsorption of the first PTCDA layer quenches the intrinsic surface plasmon originated from the clean Ag(111). When the second layer is formed, fluorescence spectra are dominated by the signals from PTCDA, which are interpreted as the radiative decay from the manifold of first singlet excited state (S(1)) of adsorbed PTCDA. The fluorescence of PTCDA is independent of the bias polarity. In addition, the fluorescence excitation spectrum agrees with that by optical excitation. Both results indicate that S(1) is directly excited by the inelastic impact scattering of electrons tunneling within the PTCDA adlayer.
通过扫描隧道显微镜（STM）中的原位荧光光谱，研究了隧穿电子诱导进入Ag(111)上3,4,9,10-苝四羧酸二酐（PTCDA）吸附层的电子激发。表面的微小区域通过STM中的电子隧穿过程被激发。荧光光谱强烈依赖于Ag(111)上PTCDA的覆盖度。第一层PTCDA的吸附淬灭了源自清洁Ag(111)的本征表面等离子体激元。当形成第二层时，荧光光谱由PTCDA的信号主导，这被解释为吸附的PTCDA第一单重激发态（S(1)）的多重态的辐射衰减。PTCDA的荧光与偏压极性无关。此外，荧光激发光谱与光激发光谱一致。这两个结果表明，S(1)是由PTCDA吸附层内隧穿电子的非弹性碰撞散射直接激发的。
