Gollub C, Korff B M R, Kompa K L, de Vivie-Riedle R
LMU Department Chemie, Butenandt-Str. 11, 81377 München, Germany.
Phys Chem Chem Phys. 2007 Jan 21;9(3):369-76. doi: 10.1039/b612286h. Epub 2006 Nov 21.
In this theoretical study vibrational ladder climbing in transition metal carbonyl complexes, as a possible means to initialize chemical ground state reactions, and the resulting vibrational population distribution using chirped mid-infrared femtosecond laser pulses is investigated. Our model system is MnBr(CO)(5), a strong IR-absorber within an experimentally easily accessible wavelength region. Special emphasis is put on the perturbation due to additional vibrational modes, especially on one, which allows dissociation at low energies. The related potential energy surface for the three representative modes is calculated, whereon quantum dynamics calculations, including the laser-molecule interaction, are performed. No significant coupling could be detected, neither in the bound, nor in the dissociative region. Contrarily, we found a dynamical barrier even for energies high above the dissociation limit. Different vibrational population distributions after the laser excitation of the CO stretching mode could be generated in dependence of the chirp parameters. Based on these findings we simulated the laser excitation corresponding to an experiment by M. Joffre et al., Proc. Natl. Acad. Ssi. U. S. A., 2004, 101(36), 13216-13220, where coherent vibrational ladder climbing in carboxyhemoglobin was demonstrated and we could offer an explanation for an open question, concerning the interpretation of the spectroscopic data.
在这项理论研究中，我们研究了过渡金属羰基配合物中的振动阶梯爬升，将其作为引发化学基态反应的一种可能手段，并研究了使用啁啾中红外飞秒激光脉冲产生的振动布居分布。我们的模型体系是MnBr(CO)(5)，它在实验上易于获得的波长区域内是一种强红外吸收体。特别强调了由于额外振动模式引起的微扰，尤其是对一种能在低能量下发生解离的模式。计算了三种代表性模式的相关势能面，并在其上进行了包括激光-分子相互作用的量子动力学计算。在束缚区域和解离区域均未检测到明显的耦合。相反，我们发现即使对于远高于解离极限的能量也存在一个动力学势垒。根据啁啾参数的不同，可以在CO伸缩模式的激光激发后产生不同的振动布居分布。基于这些发现，我们模拟了与M. Joffre等人发表于《美国国家科学院院刊》2004年第101卷第36期第13216 - 13220页的一项实验相对应的激光激发过程，该实验展示了羧基血红蛋白中的相干振动阶梯爬升，并且我们能够对一个关于光谱数据解释的开放性问题给出解释。
