Effects of large first-order static quadrupole splittings on 1/2 → -1/2 exponential spin-resonance decay rates

The effects of intraspin cross relaxation induced by first-order static quadrupole fields on the decay rate of the 1/2 → -1/2 spin resonance transition is investigated in the limit where the other $\frac{1}{2}\nrightarrow -\frac{1}{2}$ transitions are shifted in frequency by much more than intrinsic decay rates. In particular, we calculate the ratio of the decay rate for the 1/2 → -1/2 transition to the usual decay rate $\frac{1}{T_2}$ for some exponential decay mechanisms including several spin-lattice relaxation processes and motionally narrowed dipolar decay. Ratios of multipole decay rates for the above mechanisms are calculated for half-integer spins with values of $I$ up to 9/2.