Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA.
Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
J Chem Phys. 2019 Mar 14;150(10):101102. doi: 10.1063/1.5090508.
Electronic spin-state dynamics were studied for a series of Au(SCH) and AuPd(SCH) monolayer-protected clusters (MPCs) prepared in a series of oxidation states, q, including q = -1, 0, +1. These clusters were chosen for study because Au(SCH) is a closed-shell superatomic cluster, but Au(SCH) is an open-shell (7-electron) system; Au(SCH) and PdAu(SCH) are isoelectronic (6-electron) closed-shell systems. Carrier dynamics for electronic fine structure spin states were isolated using femtosecond time-resolved circularly polarized transient-absorption spectroscopy (fs-CPTA). Excitation energies of 1.82 eV and 1.97 eV were chosen for these measurements on Au(SCH) in order to achieve resonance matching with electronic fine structure transitions within the superatomic P- and D-orbital manifolds; 1.82-eV excited an unpaired P electron to D states, whereas 1.97-eV was resonant with transitions between filled P and P subshells and higher-energy D orbitals. fs-CPTA measurements revealed multiple spin-polarized transient signals for neutral (open shell) Au(SCH), following 1.82-eV excitation, which persisted for several picoseconds; time constants of 5.03 ± 0.38 ps and 2.36 ± 0.59 ps were measured using 2.43 and 2.14 eV probes, respectively. Polarization-dependent fs-CPTA measurements of PdAu(SCH) clusters exhibit no spin-conversion dynamics, similar to the isoelectronic Au(SCH) counterpart. These observations of cluster-specific dynamics resulted from spin-polarized superatom P to D excitation, via an unpaired P electron of the open-shell seven-electron Au(SCH) MPC. These results suggest that MPCs may serve as structurally well-defined prototypes for understanding spin and quantum state dynamics in nanoscale metal systems.
电子自旋态动力学研究了一系列 Au(SCH) 和 AuPd(SCH) 单层保护的团簇(MPCs),这些团簇在一系列氧化态 q 中制备,包括 q = -1、0、+1。选择这些团簇进行研究是因为 Au(SCH) 是一个闭壳超原子团簇,但 Au(SCH) 是一个开壳(7 电子)系统;Au(SCH) 和 PdAu(SCH) 是等电子(6 电子)闭壳系统。使用飞秒时间分辨圆偏振瞬态吸收光谱(fs-CPTA)分离电子精细结构自旋态的载流子动力学。选择 1.82 eV 和 1.97 eV 的激发能对 Au(SCH) 进行这些测量,以便与超原子 P 和 D 轨道能级内的电子精细结构跃迁实现共振匹配;1.82 eV 将不成对的 P 电子激发到 D 态,而 1.97 eV 与填充的 P 和 P 亚壳之间以及高能 D 轨道的跃迁共振。fs-CPTA 测量显示,中性(开壳)Au(SCH) 在 1.82 eV 激发后,有多个自旋极化瞬态信号,持续数皮秒;使用 2.43 和 2.14 eV 探针分别测量到的时间常数为 5.03 ± 0.38 ps 和 2.36 ± 0.59 ps。PdAu(SCH) 团簇的偏振相关 fs-CPTA 测量没有自旋转换动力学,类似于等电子的 Au(SCH) 对应物。这些观察到的团簇特异性动力学是由于自旋极化超原子 P 到 D 的激发,通过开壳七电子 Au(SCH) MPC 的不成对 P 电子。这些结果表明,MPCs 可能作为结构上定义良好的原型,用于理解纳米尺度金属系统中的自旋和量子态动力学。
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