抄録
The effect of a strong transverse field of frequency ω1 and amplitude H1 on the dipolar line width of the nuclear magnetic resonance signal, has been calculated. The resonance signal is supposed to be the response of a weak transverse rf field varying with frequency ω2. By choosing the value of ω1 such that γH1=\sqrt2(\barω−ω1) where \barω is the average Larmor frequency of spins with the same gyromagnetic ratios γ, it is shown that in solids for γH1>>Cst where Cst is the frequency corresponding to the static dipolar line width in the absence of the strong rf field, the width can be reduced to the order of magnitude Cst2⁄γH1. In the case of liquids with 1⁄τc>>Cst, where τc is the correlation time of the molecular fluctuations, the line width is already reduced even with only the weak rf field by a factor τcCst compared to that of solids; and to achieve further narrowing the same condition for ω1 as in solids is required and a still stronger condition γH1>>1⁄τc for H1.
