Weak Irradiation Effect on the Inversion-Recovery Process of a ¹³C--¹H Spin System. II. Nonselective Inversion

Abstract

Recoveries after nonselective inversion of the ¹³C lines in a coupled ¹³C-¹H spin system are observed under the just-resonance irradiation to one of the ¹H doublet lines. The irradiating rf field is not too strong to result in any appreciable splitting of the observed lines. Only for a line connected progressively to the stirred one, the recovery can considerably be accelerated when the rf is strong enough to partially saturate absorption of the stirred one. On the other hand, the recovery for another regressively-connected line is extremely retarded by the rf field with similar amplitudes. The contrasting changes in the recoveries are attributed to the opposite coherent and incoherent effects of the relatively strong rf field for the two connected combinations of the stirred and observed lines. These results are discussed by the use of relaxation modes in the recovery process.