Site-dependent spectral shifts in core-to-pi* excitations of pyridine clusters.
Site-dependent spectral shifts in core-to-pi* excitations of pyridine clusters.
复制标题
吡啶簇的核心到 pi* 激发的位点依赖性光谱变化。
DOI：
--
复制
发表时间：
2008
影响因子：
2.9
通讯作者：
Eckart Rühl
中科院分区：
文献类型：
--
作者：
I. Bradeanu;Nobuhiro Kosugi;R. Flesch;Eckart Rühl
研究了自由吡啶原子团簇中中心到pi*的位置和元素选择性激发。实验结果表明，在C1s和N1s->；pi*激发区发生了位置和尺寸相关的光谱漂移。具体地说，我们在C1S区观察到团簇中C1S-->；pi*带的低能斜率相对于裸分子发生了显著的、与位置相关的红移90 meV，而该带的高能斜率几乎保持不变。相反，在整个N1S-->；pi*带中发现了与尺寸相关的相同量级的蓝移。这与之前关于van der Waals团簇的结果截然不同，后者只在1s->；pi*跃迁中观察到红移。实验结果与用于模拟1s->；pi*(v=0)跃迁的从头计算结果进行了比较。这些结果清楚地表明，光谱位移主要是分子部分之间静电相互作用的结果，在可变大小的吡啶簇合物中，分子单元的反平行取向优选地占主导地位。
Site- and element-selective core-to-pi* excitation in free pyridine clusters is investigated. The experimental results indicate the occurrence of site- and size-dependent spectral shifts in the C 1s and N 1s --> pi* excitation regime. Specifically, we observe in the C 1s regime a substantial and site-dependent redshift of the low energy slopes of the C 1s --> pi* band by 90 meV in clusters relative to the bare molecule, whereas the high energy slopes of this band remain almost unchanged. In contrast, a size-dependent blueshift of the same order of magnitude is found for the entire N 1s --> pi* band. This is distinctly different from previous results on van der Waals clusters, where exclusively redshifts in 1s --> pi* transitions are observed. The experimental results are compared to ab initio calculations, which serve to simulate the 1s --> pi*( v = 0) transitions. These results clearly indicate that the spectral shifts are primarily a result of electrostatic interactions between the molecular moieties and that an antiparallel orientation of molecular units preferably dominates in variable-size pyridine clusters.