Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana, 47907-2084, USA.
J Phys Chem A. 2011 Aug 18;115(32):8895-905. doi: 10.1021/jp2043202. Epub 2011 Jul 25.
Two-dimensional (2D) correlation techniques are developed for chirped-pulse Fourier transform microwave (CP-FTMW) spectroscopy. The broadband nature of the spectrometer coupled with fast digital electronics permits the generation of arbitrary pulse sequences and simultaneous detection of the 8-18 GHz region of the microwave spectrum. This significantly increases the number of rotation transitions that can be simultaneously probed, as well as the bandwidth in both frequency dimensions. We theoretically and experimentally evaluate coherence transfer of three- and four-level systems to relate the method with previous studies. We then extend the principles of single-quantum and autocorrelation to incorporate broadband excitation and detection. Global connectivity of the rotational energy level structure is demonstrated through the transfer of multiple coherences in a single 2D experiment. Additionally, open-system effects are observed from irradiating many-level systems. Quadrature detection in the indirectly measured frequency dimension and phase cycling are also adapted for 2D CP-FTMW spectroscopy.
发展了用于啁啾脉冲傅里叶变换微波（CP-FTMW）光谱学的二维（2D）相关技术。光谱仪的宽带特性与快速数字电子技术相结合，允许生成任意脉冲序列，并同时检测微波光谱的 8-18GHz 区域。这显著增加了可以同时探测的旋转跃迁的数量，以及在两个频率维度上的带宽。我们从理论和实验上评估了三能级和四能级系统的相干转移，以将该方法与以前的研究联系起来。然后，我们将单量子和自相关的原理扩展到包含宽带激发和检测。通过在单个 2D 实验中传递多个相干，可以证明旋转能级结构的全局连通性。此外，从多能级系统的辐照中观察到开系统效应。在间接测量的频率维度中采用正交检测和相位循环，也适用于 2D CP-FTMW 光谱学。
