In the present work, Herzberg–Teller selection rules on the charge-transfer (CT) effect in surface-enhanced Raman spectroscopy (SERS) are explored for the 3,4,9,10-perylene tetracarboxylic diimide (PTCDI) adsorbed on the Ag nano-island film (AgNIF) using several Raman excitation wavelengths. The UV/VIS/NIR spectrum of PTCDI adsorbed on the AgNIF indicates that excitation wavelengths of 514.5 nm, 633 nm, and 785 nm are in resonance with CT states of the complex, PTCDI adsorbed on the AgNIF. This CT resonance results in intensity enhancement of non-totally symmetric vibrational modes with b₁ symmetry in SERS. The three resonances (molecular, localized surface plasmon, and charge transfer) are observed for SERS with 514.5 nm. The totally symmetric Raman bands with symmetry a₁ exhibit maximum enhancement in SERS with a 514.5 nm wavelength and suggest the maximum electromagnetic mechanism in SERS with 514.5 nm. Few Raman-forbidden modes and silent modes are allowed in the SERS spectra due to the reduced symmetry of PTCDI in the proximity of the AgNIF. Moreover, density functional theory computation is also carried out to calculate vibrational modes and electronic transitions.

中文翻译：

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依赖于激发波长的SERS和DFT研究来探索荷兹伯格-泰勒电荷转移效应的选择规则。

在目前的工作中，针对吸附在Ag上的3,4,9,10-per四羧酸二酰亚胺（PTCDI），探索了关于表面增强拉曼光谱（SERS）中电荷转移（CT）效应的Herzberg-Teller选择规则。纳米岛薄膜（AgNIF）使用几种拉曼激发波长。吸附在AgNIF上的PTCDI的UV / VIS / NIR光谱表明，激发波长为514.5 nm，633 nm和785 nm与复合物PTCDI吸附在AgNIF上的CT状态共振。该CT共振导致SERS中具有b ₁对称性的非完全对称振动模式的强度增强。对于具有514.5nm的SERS，观察到三个共振（分子共振，局部表面等离子体激元和电荷转移）。对称为a ₁的完全对称拉曼谱带在514.5 nm波长的SERS中显示出最大的增强，并在514.5 nm的SERS中显示出最大的电磁机理。由于AgNIF附近PTCDI的对称性降低，因此在SERS光谱中几乎不允许使用拉曼禁能模式和静音模式。此外，还进行了密度泛函理论计算以计算振动模式和电子跃迁。