Frequency Dependence of Gd III Electronic Relaxation in Aqueous Solution

Complex Peak-to-peak linewidth (mT) Tie measured (ns) Tie predicted (ns) 

Treatments to interpret the frequeney dependenee of Tie and Tje have become inereasingly sophisticated. The multifrequency studies done in solution define a funetion of zero-field splitting (ZFS) or the crystal-field interaction cfi) parameters, denoted as A. The relationship between the parameters D and E, whieh account for the quadrupolar part of the cfr, and is defined as A = 2I3)D + 2E. The cfi parameters for Gd(III) complexes are dealt with in mueh more detail below in Section 3, where we discuss more reeent results on frozen glassy solutions. Here we describe efforts to understand eleetronic relaxation in solution and how this impacts nuclear magnetic relaxation and MRI contrast agents. 

Hudson and Lewis [20] showed that the eigenvalues of the relaxation matrix R as defined in Bloeh-Wangsness-Redfield theory [21 ] are functions of a correlation time Tv and the experimental ffequeney cOs, and are related to the relaxation time 7 2ei of the fth allowed eleetron spin transition by 

Values of A obtained in this manner are very similar to those obtained from line-shape analysis. This approach was further extended by Borel et al. [23] to include 

ARNOLD M. RAITSIMRING. ANDREI V. ASTASHKIN, and PETER CARAVAN 

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