Wavelet analysis of nuclear magnetic resonance signal characteristics

The wavelet energy spectrum was proposed to analyze nuclear magnetic resonance signal characteristics. This paper focused on the intermolecular multiple quantum coherence and radiation damping signal for they had similar Fourier spectra. The free induced decay signals originating from the intermolecular double quantum coherence and radiation damping are demonstrated by both experiments and simulations. Compared with the Fourier spectrum, the wavelet energy spectrum revealed the signal intensity is not only related with time but also with frequency. Relevant characteristics of the wavelet energy spectrum, such as the maximum energy, the corresponding moment and the total energy were investigated in detail. As for intermolecular double quantum coherence, the maximum and total energy reaches the top when the optimal flip angle is applied. Moreover, the maximum moments are the same irrespective of the different flip angles. With regard to radiation damping, the energy achieves maximum when the flip angle is 90deg, and the larger the flip angle is, the more the total energy is and the longer the acquiring moment is.