Nanoscience Center, Department of Chemistry, P. O. Box 35, FI-40014 University of Jyväskylä, Finland.
J Phys Chem A. 2013 Jun 13;117(23):4884-97. doi: 10.1021/jp402732b. Epub 2013 May 24.
The absorption spectrum of I2 in solid Xe shows resolved zero-phonon lines and phonon side bands near the origin of the B←X transition (550-625 nm). The long-lived |B⟩⟨X| coherence in this energy range (T2 = 600 fs on average) emerges as vibrationally unrelaxed fluorescence in resonance Raman (RR) spectra. Upon excitation in the structureless continuum at 532 nm, the oscillatory RR progression exhibits electronic dephasing time of T2 = 150 fs. Two RR progressions with markedly different vibrational coherence on the X-state are observed. The main progression of sharp overtones (T2 > 21 ps) is assigned to molecules trapped in double-substitution sites. The minor progression, which shows dephasing times T2 = 6-0.6 ps for v = 1-8, is assigned to molecules in triple-substitution sites. The line progressions allow a detailed characterization of the solvated B- and X-state potentials. Time-resolved coherent anti-Stokes Raman scattering is used to probe selected vibrational coherences on the X-state. Assignments are obtained through molecular dynamics simulations, which reproduce the relative dephasing rates between the two sites, clarify the role of rotation-translation dynamics, and enable quantum dynamics simulations of the spectra by the potentials of mean force that accurately describe the molecule-surrounding interactions.
I2 在固体 Xe 中的吸收光谱在 B←X 跃迁（550-625nm）的原点附近显示出分辨的零声子线和声子边带。在这个能量范围内（平均 T2 = 600fs），|B⟩⟨X|长寿命相干性以非振动弛豫的荧光出现在共振拉曼（RR）光谱中。在 532nm 的无结构连续体中激发时，振荡的 RR 进展表现出电子退相时间 T2 = 150fs。在 X 态上观察到两个具有明显不同振动相干性的 RR 进展。主要的泛音（T2 > 21ps）进展归因于被困在双取代位的分子。次要进展显示 T2 = 6-0.6ps（v = 1-8）的退相时间，归因于三重取代位的分子。线进展允许对溶剂化 B 和 X 态势进行详细表征。时间分辨相干反斯托克斯拉曼散射用于探测 X 态上的选定振动相干性。通过分子动力学模拟获得了分配，该模拟再现了两个位点之间的相对退相速率，阐明了旋转-平移动力学的作用，并通过准确描述分子-周围相互作用的平均力势来实现对光谱的量子动力学模拟。
