Department of Chemistry, Inha University , Incheon 402-751, South Korea.
Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK) , 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan.
Struct Dyn. 2016 Apr 29;3(4):043209. doi: 10.1063/1.4948516. eCollection 2016 Jul.
The [Au(CN)2 (-)]3 trimer in water experiences a strong van der Waals interaction between the d(10) gold atoms due to large relativistic effect and can serve as an excellent model system to study the bond formation process in real time. The trimer in the ground state (S0) exists as a bent structure without the covalent bond between the gold atoms, and upon the laser excitation, one electron in the antibonding orbital goes to the bonding orbital, thereby inducing the formation of a covalent bond between gold atoms. This process has been studied by various time-resolved techniques, and most of the interpretation on the structure and dynamics converge except that the structure of the first intermediate (S1) has been debated due to different interpretations between femtosecond optical spectroscopy and femtosecond X-ray solution scattering. Recently, the excitation wavelength of 267 nm employed in our previous scattering experiment was suggested as the culprit for misinterpretation. Here, we revisited this issue by performing femtosecond X-ray solution scattering with 310 nm excitation and compared the results with our previous study employing 267 nm excitation. The data show that a linear S1 structure is formed within 500 fs regardless of excitation wavelength and the structural dynamics observed at both excitation wavelengths are identical to each other within experimental errors.
在水中，[Au(CN)2 (-)]3 三聚体由于较大的相对论效应，其 d(10)金原子之间存在强烈的范德华相互作用，可以作为一个极好的模型体系，用于实时研究键形成过程。基态 (S0) 中的三聚体呈弯曲结构，金原子之间没有共价键，而在激光激发下，反键轨道上的一个电子跃迁到成键轨道，从而诱导金原子之间形成共价键。这一过程已经通过各种时间分辨技术进行了研究，除了由于飞秒光学光谱和飞秒 X 射线溶液散射之间的不同解释，第一个中间物 (S1) 的结构存在争议外，大多数对结构和动力学的解释已经趋于一致。最近，我们之前散射实验中使用的 267nm 激发波长被认为是导致误解的罪魁祸首。在这里，我们通过使用 310nm 激发进行飞秒 X 射线溶液散射实验重新研究了这个问题，并将结果与我们之前使用 267nm 激发的研究进行了比较。数据表明，无论激发波长如何，线性 S1 结构在 500fs 内形成，并且在两个激发波长下观察到的结构动力学在实验误差范围内彼此相同。
