An efficient double-tuned 13C/ 1H probe circuit for CP/MAS NMR and its importance in linewidths

Abstract

A simple double-tuned 13 C 1 H probe for high-field CP/MAS NMR is described. The to 50 ω. Isolation between 1H and 13C channels exceeds 40 dB. The sensitivity ( S N ) of the observation channel ( 13C) for methyl carbons is close to 47 in a CP/MAS experiment of 10 scans on 70 mg of a sample of hexamethylbenzene for the rotor sample volume of 140 μl. The probe delivers a 2.4 μs 90° proton pulse with only 90 W at 200 MHz and 250 W at 50.3 MHz. Examples are presented of linewidth reduction with higher decoupling power. The effects of anisotropy in the bulk magnetic susceptibility are also discussed.