Wright John C
Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706; email:
Annu Rev Anal Chem (Palo Alto Calif). 2017 Jun 12;10(1):45-70. doi: 10.1146/annurev-anchem-061516-045349. Epub 2017 Mar 27.
A new family of vibrational and electronic spectroscopies has emerged, comprising the coherent analogs of traditional analytical methods. These methods are also analogs of coherent multidimensional nuclear magnetic resonance (NMR) spectroscopy. This new family is based on creating the same quantum mechanical superposition states called multiple quantum coherences (MQCs). NMR MQCs are mixtures of nuclear spin states that retain their quantum mechanical phase information for milliseconds. The MQCs in this new family are mixtures of vibrational and electronic states that retain their phases for picoseconds or shorter times. Ultrafast, high-intensity coherent beams rapidly excite multiple states. The excited MQCs then emit bright beams while they retain their phases. Time-domain methods measure the frequencies of the MQCs by resolving their phase oscillations, whereas frequency-domain methods measure the resonance enhancements of the output beam while scanning the excitation frequencies. The resulting spectra provide multidimensional spectral signatures that increase the spectroscopic selectivity required for analyzing complex samples.
一个新的振动和电子光谱学家族出现了，它由传统分析方法的相干类似物组成。这些方法也是相干多维核磁共振（NMR）光谱学的类似物。这个新家族基于创建相同的量子力学叠加态，即所谓的多量子相干（MQC）。NMR MQC是核自旋态的混合物，能在数毫秒内保留其量子力学相位信息。这个新家族中的MQC是振动和电子态的混合物，能在皮秒或更短时间内保留其相位。超快、高强度的相干光束能快速激发多个态。被激发的MQC在保留其相位时会发射明亮的光束。时域方法通过解析其相位振荡来测量MQC的频率，而频域方法在扫描激发频率时测量输出光束的共振增强。所得光谱提供了多维光谱特征，增加了分析复杂样品所需的光谱选择性。
