1H13C polarization transfer via the nuclear solid effect
Abstract
1H13C polarization transfer via the nuclear solid effect (NSE) is investigated. Polarization transfer is obtained via irradiation at a frequency equal to the difference or sum of the proton and carbon Larmor frequencies, the "forbidden" transitions. 13C spectra of polyethylene, polypropylene, and hexamethylbenzene obtained by NSE, conventional cross-polarization, and thermal polarization are shown. It is found that for direct CH bonds the intensities of the 13C NSE spectra are often considerably larger than those of the spectra obtained by the cross-polarization method, and also provide more quantitative information. The 13C signals due to indirect CH bonds are suppressed in the NSE case, mainly due to the technological problem of the heating due to the finite high-power irradiation time at the forbidden transition. Experiments to alleviate these problems are proposed. © 1987.