Department of Chemistry, McGill University, Montreal, Quebec H3A 0G4, Canada.
J Chem Phys. 2023 Feb 28;158(8):084201. doi: 10.1063/5.0138252.
Two-dimensional electronic spectroscopy (2DES) has recently been gaining popularity as an alternative to the more common transient absorption spectroscopy due to the combination of high frequency and time resolution of 2DES. In order to advance the reliable analysis of population dynamics and to optimize the time resolution of the method, one has to understand the numerous field matter interactions that take place at an early and negative time. These interactions have historically been discussed in one-dimensional spectroscopy as coherent artifacts and have been assigned to both resonant and non-resonant system responses during or before the pulse overlap. These coherent artifacts have also been described in 2DES but remain less well-understood due to the complexity of 2DES and the relative novelty of the method. Here, we present 2DES results in two model nanocrystal samples, CdSe and CsPbI. We demonstrate non-resonant signals due to solvent response during the pulse overlap and resonant signals, which we assign to perturbed free induction decay (PFID), both before and during the pulse overlap. The simulations of the 2DES response functions at early and negative time delays reinforce the assignment of the negative time delay signals to PFID. Modeling reveals that the PFID signals will severely distort the initial picture of the resonant population dynamics. By including these effects in models of 2DES spectra, one is able to push forward the extraction of early time dynamics in 2DES.
二维电子光谱学（2DES）最近由于其具有高频和时间分辨率的特点，已经成为一种替代更常见的瞬态吸收光谱学的方法而受到关注。为了推进对种群动力学的可靠分析，并优化该方法的时间分辨率，人们必须了解在早期和负时间发生的大量场物质相互作用。这些相互作用在一维光谱学中一直被讨论为相干伪影，并在脉冲重叠期间或之前被分配给共振和非共振系统响应。这些相干伪影也在 2DES 中进行了描述，但由于 2DES 的复杂性和该方法的相对新颖性，它们仍然不太被理解。在这里，我们在两个模型纳米晶体样品（CdSe 和 CsPbI）中展示了 2DES 结果。我们演示了由于在脉冲重叠期间溶剂响应而产生的非共振信号，以及在脉冲重叠之前和期间我们归因于受扰自由感应衰减（PFID）的共振信号。在早期和负时间延迟处的 2DES 响应函数的模拟加强了对负时间延迟信号归因于 PFID 的推断。建模表明，PFID 信号将严重扭曲共振种群动力学的初始图像。通过在 2DES 光谱的模型中包含这些效应，人们能够在 2DES 中推进早期动力学的提取。
