University of Groningen, Zernike Institute for Advanced Materials, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
Phys Chem Chem Phys. 2018 May 9;20(18):12746-12754. doi: 10.1039/c8cp00638e.
In rhodopsin, the absorption of a photon causes the isomerization of the 11-cis isomer of the retinal chromophore to its all-trans isomer. This isomerization is known to occur through a conical intersection (CI) and the internal conversion through the CI is known to be vibrationally coherent. Recently measured two-dimensional electronic spectra (2DES) showed dramatic absorptive spectral features at early waiting times associated with the transition through the CI. The common two-state two-mode model Hamiltonian was unable to elucidate the origin of these features. To rationalize the source of these features, we employ a three-state three-mode model Hamiltonian where the hydrogen out-of plane (HOOP) mode and a higher-lying electronic state are included. The 2DES of the retinal chromophore in rhodopsin are calculated and compared with the experiment. Our analysis shows that the source of the observed features in the measured 2DES is the excited state absorption to a higher-lying electronic state and not the HOOP mode.
在视紫红质中，光子的吸收导致视黄醛发色团的 11-顺式异构体向全反式异构体的异构化。这种异构化已知通过锥形交叉（CI）发生，并且通过 CI 的内部转换已知是振动相干的。最近测量的二维电子光谱（2DES）在与通过 CI 的跃迁相关的早期等待时间显示出明显的吸收光谱特征。常见的双态双模模型哈密顿量无法阐明这些特征的起源。为了合理化这些特征的来源，我们采用了一个三态三模模型哈密顿量，其中包括氢出平面（HOOP）模式和更高的电子态。计算了视黄醛在视紫红质中的 2DES，并与实验进行了比较。我们的分析表明，测量的 2DES 中观察到的特征的来源是激发态吸收到更高的电子态，而不是 HOOP 模式。
