Weak Irradiation Effect on the Inversion-Recovery Process of a ¹³C–¹H Spin System. I. Selective Inversion

Abstract

The recovery after selective inversion of a ¹³C-line in a coupled ¹³C–¹H spin system in ¹³C-enriched formic acid is observed under the just-resonance irradiation to one of the ¹H-doublet lines. The continuous rf is not too strong to result in any appreciable splitting of the observed line. It is found that only the recovery of a line which is progressively connected to the stirred one can considerably be accelerated by the rf when it partially, not completely, saturate absorption of the stirred line. The acceleration is due to both of coherent and incoherent effects of the rf, while the latter one considerably retards the recovery for regressively-connected combinations of the observed and stirred lines. A detailed account of these phenomena based on a relaxation-mode analysis of the recovery process is given.