The modulated gradient spin echo is an NMR method that provides direct insight into the low-frequency part of the molecular velocity auto-correlation spectra in fluids. Because the method gives a spectrum that is time-averaged over the trajectory elapsed, the spins are able to observe local inhomogeneities in the initial interval after spin excitation. In fluid measurements, it manifests as an initial non-exponential decay of the spin-echo signals, which we attribute to the spatial heterogeneity of molecular self-diffusion due to the molecular motion in microvortices of hydrodynamic oscillations. The hydrodynamic fluctuations occur in water, ethanol, toluene, and a mixture of water with lower glycerol content, while they disappeared with increasing glycerol content.

调制梯度自旋回波是一种NMR方法，可提供对流体中分子速度自相关谱的低频部分的直接了解。由于该方法给出的光谱在经过的轨迹上是时间平均的，因此自旋能够在自旋激发后的初始间隔中观察到局部不均匀性。在流体测量中，它表现为自旋回波信号的初始非指数衰减，这归因于分子自扩散的空间异质性，这归因于流体动力振荡的微涡旋中的分子运动。水动力波动发生在水，乙醇，甲苯和甘油含量较低的水的混合物中，而随着甘油含量的增加而消失。