Pulse Propagation Effects in Optical 2D Fourier-Transform Spectroscopy: Theory
Pulse Propagation Effects in Optical 2D Fourier-Transform Spectroscopy: Theory
复制标题
光学二维傅立叶变换光谱中的脉冲传播效应：理论
DOI：
10.1021/acs.jpca.5b00001
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
Jonas, David M.
中科院分区：
文献类型：
--
作者：
Spencer, Austin P.;Li, Hebin;Cundiff, Steven T.;Jonas, David M.
本文用三维频域求解麦克斯韦方程组的方法计算了铷原子蒸气在氩气缓冲气体中D2线的重相位二维傅里叶变换谱。从脉冲通过样品的空间传播的实验失真模拟在2DFT光谱计算的均匀布洛赫线形模型。出现在光密度高达3的光谱特征进行了研究。随着光密度的增加，吸收和色散畸变开始于峰形加宽，进展到峰分裂，并最终导致分裂峰的先前未探索的相干瞬态扭曲。与低光密度限制相反，其中布洛赫模型的2D峰形仅取决于总的退相时间，在有限光密度下的2D峰形的这些失真通过相干瞬态效应随着等待时间和激发态寿命而变化。实验的具体条件进行了探讨，展示了不同的光束重叠内的样品和伪时域滤波的影响。对于在样品入口处开始的光束重叠，减小光束重叠的长度减小了沿着ωτ轴的线宽，但也减小了信号强度。伪时域滤波器（其中从FID参考的2D信号中排除最后激励脉冲的中心之前的信号）减小了沿沿着ω走向的传播失真。它表明，2DFT重定相谱不能利用的激发检测变换，可以消除传播失真2DFT弛豫谱。最后，将氩缓冲气体中铷蒸气的高光密度实验2DFT光谱[J. Phys. Chem. A 2013，117，6279 - 6287]在线宽、峰分裂深度和相干瞬态峰扭曲方面与光密度高于报道的模拟进行定量比较。
A solution to Maxwell’s equations in the three-dimensional frequency domain is used to calculate rephasing two-dimensional Fourier transform (2DFT) spectra of the D2line of atomic rubidium vapor in argon buffer gas. Experimental distortions from the spatial propagation of pulses through the sample are simulated in 2DFT spectra calculated for the homogeneous Bloch line shape model. Spectral features that appear at optical densities of up to 3 are investigated. As optical density increases, absorptive and dispersive distortions start with peak shape broadening, progress to peak splitting, and ultimately result in a previously unexplored coherent transient twisting of the split peaks. In contrast to the low optical density limit, where the 2D peak shape for the Bloch model depends only on the total dephasing time, these distortions of the 2D peak shape at finite optical density vary with the waiting time and the excited state lifetime through coherent transient effects. Experiment-specific conditions are explored, demonstrating the effects of varying beam overlap within the sample and of pseudo-time domain filtering. For beam overlap starting at the sample entrance, decreasing the length of beam overlap reduces the line width along the ωτaxis but also reduces signal intensity. A pseudo–time domain filter, where signal prior to the center of the last excitation pulse is excluded from the FID-referenced 2D signal, reduces propagation distortions along the ωtaxis. It is demonstrated that 2DFT rephasing spectra cannot take advantage of an excitation–detection transformation that can eliminate propagation distortions in 2DFT relaxation spectra. Finally, the high optical density experimental 2DFT spectrum of rubidium vapor in argon buffer gas [J. Phys. Chem. A 2013, 117, 6279−6287] is quantitatively compared, in line width, in depth of peak splitting, and in coherent transient peak twisting, to a simulation with optical density higher than that reported.