Choi Jun-Ho, Cho Minhaeng
Department of Chemistry and Center for Multidimensional Spectroscopy, Korea University, Seoul 136-701, Korea.
J Phys Chem A. 2007 Jun 21;111(24):5176-84. doi: 10.1021/jp0687044. Epub 2007 May 25.
A coherent two-dimensional (2D) optical spectroscopy utilizing circularly polarized (CP) beams, which was shown to be useful in studying molecular chirality in condensed phases, was theoretically proposed recently [Cho et al. J. Chem. Phys. 2003, 119, 7003]. A photon echo (PE) version of 2D optical activity spectroscopy is discussed in this paper. Considering various dipeptide and polypeptide systems, where the amide I local modes constitute the set of basis modes used to describe exciton and biexciton states as linear combinations of those basis modes, we present numerically simulated 2D circularly polarized IR PE spectra. It is shown that this novel spectroscopic method can provide additional information on the angles between the transition magnetic dipole and the transition electric dipole of two different vibrationally excited states, which are highly sensitive to the 3D structure and chirality of a given polypeptide. Also, a hierarchical relation of IR absorption, vibrational circular dichroism, 2D IR PE, and 2D CP-IR PE is discussed to show advantages of 2D optical activity spectroscopy in general.
一种利用圆偏振（CP）光束的相干二维（2D）光学光谱，最近在理论上被提出，它被证明在研究凝聚相中的分子手性方面很有用[Cho等人，《化学物理杂志》，2003年，第119卷，第7003页]。本文讨论了二维光学活性光谱的光子回波（PE）版本。考虑到各种二肽和多肽系统，其中酰胺I局部模式构成用于将激子和双激子态描述为这些基模线性组合的基模集，我们给出了数值模拟的二维圆偏振红外光子回波光谱。结果表明，这种新颖的光谱方法可以提供关于两个不同振动激发态的跃迁磁偶极子和跃迁电偶极子之间角度的额外信息，这些角度对给定多肽的三维结构和手性高度敏感。此外，还讨论了红外吸收、振动圆二色性、二维红外光子回波和二维圆偏振红外光子回波之间的层次关系，以总体展示二维光学活性光谱的优势。
