Relaxation rate minimal value

Ru dihydride [in the absence of (CF3)2CHOH], and the Ti,min (RuH H) is a minimal relaxation time of the hydride ligand that is involved in dihydrogen bonding. The Ti min CRuH- H) value is calculated from eq. (4.11) as 0.0894 s. This time is remarkably shorter than that in the individual dihydride (0.178 s), due to an additional hydride-proton dipolar coupling. Then this additional relaxation rate, 1/ T i min (RuH- H), governed by the single hydride-proton dipolar contact, is expressed as... 

Typically, quadrupole relaxation increases rapidly in effectiveness as Q increases, but it also depends upon the interaction of the electric quadrupole moment with the local EFG. For a fixed value of Q, this interaction is essentially geometry dependent for molecules and other structures, and it can be reduced by the minimalization of the EFG. The latter may be accomplished by situating the quadrupolar nucleus in a cubic environment (of either T or Oh symmetry). This will lead to slower relaxation rates and, therefore, narrower spectral lines with resolvable spin-spin coupling, if the latter applies. 

Fig. 26. Example of the data reduction process. Each data block of a multi-block sequence (in this case simple FIDs) is reduced to a single value by means of averaging over a predefined data window and plotted against the block s x-value. The resulting relaxation curve is then fitted to estimate its decay rate(s). The algorithm gives a lot of freedom in setting the data window and including/excluding any number of initial or final blocks. Notice that in the PP case shown here, the T-value decreases from left to right. This helps to minimize thermal variations of the magnet.

The power satnration occurs when the rate of absorption of microwave exceeds the rate at which the system returns to eqnilibrinm. A spectral parameter, R1/2, is used to describe quantitatively the microwave power saturation profile. In the RNR tyrosyl radical case, the R1/2 values at four representative temperatnres are given in Table 3. The most straightforward interpretation for the easily saturated radical spectra with very small P j2 values, as seen in M. tuberculosis R2, is that the tyrosyl radical is minimally influenced in its relaxation by the di-ferric clnster. This finding is reverse in mouse and yeast R2 proteins. To obtain the precise distance information in a biological system, advanced techniques such as ESSEM would be more pertinent than the continuous-wave EPR spectroscopy. 

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