Previously, we demonstrated that the intensities of cross peaks in a two-dimensional asynchronous spectrum could be enhanced via a change of the sequence of the corresponding 1D spectra. This unusual approach becomes useful when the determination of the sequential order of physicochemical events is not essential. However, we have not known whether the level of noise in the 2D asynchronous spectrum is also escalated as the sequence of 1D spectra is changed. Herein, we firstly investigate the noise behavior in a two-dimensional asynchronous spectrum upon changing the sequence of the corresponding 1D spectra on a model system. In the model system, bilinear data from a chromatographic-spectroscopic experiment on a mixture containing two components are analyzed via 2D asynchronous spectrum. The computer simulation results confirm that the cross peaks intensities in the resultant 2D asynchronous spectrum are indeed enhanced by more than100 times as the sequence of 1D spectra is changed, whereasthe fluctuation level of noise, reflected by the standard deviation of the value of a 2D asynchronous spectrum at a given point, is almost invariant. Further analysis on the model systems demonstrates that the special mathematical property of the Hilbert-Noda matrix (the modules of all the column vectors of the Hilbert-Noda matrix is near a constant) accounts for the moderate variation of the noise level during the changes of the sequence of 1D spectra. Secondly, a realistic example from a thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR) experiment with added artificial noise in seven 1D spectra was studied. As we alter the sequence of the seven FTIR spectra, the variation of the intensities of cross peaks covers four orders of magnitudes in the 2D asynchronous spectra. In contrast, the fluctuation of noise in 2D asynchronous spectra is within two times. The above results clearly demonstrate that a change in the sequence of 1D spectra is an effective way to improve the signal-to-noise level of the 2D asynchronous spectra.

中文翻译：

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EXPRESS：使用一维频谱序列变化增强没有噪声电平波动升级的二维异步频谱

之前，我们证明了二维异步光谱中交叉峰的强度可以通过相应一维光谱序列的变化来增强。当确定物理化学事件的顺序不是必需的时，这种不寻常的方法变得有用。然而，我们不知道二维异步频谱中的噪声水平是否也随着一维频谱序列的改变而升级。在这里，我们首先研究了在改变模型系统上相应一维频谱的序列后二维异步频谱中的噪声行为。在模型系统中，通过二维异步光谱分析对包含两种组分的混合物进行色谱-光谱实验的双线性数据。计算机模拟结果证实，随着一维频谱序列的改变，合成二维异步频谱中的交叉峰强度确实增强了 100 多倍，而噪声的波动水平，由二维异步频谱值的标准偏差反映。给定点的频谱几乎是不变的。对模型系统的进一步分析表明，Hilbert-Noda 矩阵的特殊数学性质（Hilbert-Noda 矩阵的所有列向量的模都接近于一个常数）解释了在变化过程中噪声水平的适度变化。一维光谱的序列。其次，研究了热重-傅里叶变换红外光谱 (TG-FTIR) 实验的一个现实例子，在七个一维光谱中添加了人工噪声。当我们改变七个 FTIR 光谱的顺序时，交叉峰强度的变化涵盖了二维异步光谱中的四个数量级。相比之下，二维异步频谱中的噪声波动在两倍以内。上述结果清楚地表明，改变一维光谱的序列是提高二维异步光谱信噪比的有效方法。