DOUBLE-RESONANCE DETECTION USING ZERO-FIELD LEVEL-CROSSING

Double resonance level crossing detection cannot normally be used to r ecord transitions between the quadrupole Zeeman levels. Neither can it be used if the quadrupole resonance frequency is larger than the prot on NMR frequency in high field. A simple variation of the level crossi ng experiment is demonstrated which allows energy to be efficiently tr ansferred from quadrupole to proton system and hence lead to detection in these two cases. In the case of the quadrupole Zeeman levels it al lows transitions between the +/-1/2 levels to be detected in a small m agnetic field, allowing measurement of the asymmetry parameter (eta) f or spin 3/2 systems. This is demonstrated for the B-11 nucleus in trie thanolamine berate. Detection of high frequency quadrupole transitions is demonstrated from which relaxation information is obtained.