Ultrafast lattice relaxation dynamics of photo-excited states in halogen-bridged mixed valence metal complexes

利用飞秒瞬态吸收测量研究了准一维卤素桥接混价配合物的超快弛豫动力学。在pt化合物中，观察到自俘获激子和极化子的振动激发态的产生及其向亚稳定态的弛豫过程。另一方面，发现中性孤子在时间分辨率（150fs）内产生。这被认为是由于势面的耗散性质。结果表明，随着卤素离子在pt配合物中按Cl、Br、I的顺序被取代，STE的亚稳定态弛豫的时间常数和次亚稳定态的衰减变短。发现极化子的产生效率以同样的顺序增加。这些结果被认为是由于转移能量的增加和电子-声子相互作用的减少。当钯离子取代铂离子时，极化子振动激发态的产生效率提高。这被认为是由于电子相关的增加。在pt - i化合物中发现了光生极化子和STE极化子在势面上围绕亚稳定态的波包运动振动。在mx化合物中发现了奇宇称电荷转移激子引起的强烈双光子吸收。发现响应时间在时间分辨率范围内。

Ultrafast relaxation dynamics of quasi-one-dimensional halogen-bridged mixed-valence complexes (MX-compounds) has been investigated by the femto-second transient absorption measurements. In Pt-compounds, generation of vibrational excited states of self-traped excitons (STE's) and those of polarons and their relaxation processes to the meta-stable satates have been observed. On the other hand, it was found that the neutral solitons are generated within the time resolution (150fs). It is considered to be due to the dissipative nature of the potential surfaces. It was found that the time constants of the relaxation to the meta-stable states of STE's and the decay of times meta-stable STE's become shorter as the halogen ions were replaced in the order Cl, Br, and I in Pt-complexes. The generation efficiency of polarons has bee found to increases in the same order. These results are considered to be due to the increment of transfer energy and to the decrement of electron-phonon interaction. The generation efficiency of vibrational excited states of polarons was found to increase when the platinum ions were replaced by palladium ions. This is considered to be due to the increment of electron correlation.Vibrations of wave packet motion of photo-generated polarons and those of STE's in the potential surfaces around the meta-stable states have been found in a Pt-I-compound.Intense two-photon absorption caused by charge transfer excitons with odd parity has been found in MX-compounds. The response time was found to be within the time resolution.