Millimeter magnetic spectroscopy of paramagnetic complexes Cr(V)

The obtained results of the complex spectroscopic studies of static and dynamic characteristics of the EHBA(Cr/sup V/) and HMBA(Cr/sup V/) complexes diluted in propanediol show that the maximum polarization is achieved for the paramagnetic center concentration N=0.6/spl times/10/sup 20/ - 1.2/spl times/10/sup 20/ cm/sup -3/. It has been determined that the "dynamic cooling with the burnt out hole" is the dominating mechanism of dynamic nuclear polarisation (DNP) for both complexes. However, in contrast to the HMBA(Cr/sup V/) complex the effective diffusion of nuclear spin temperature is the distinctive feature of the nuclear spin kinetics in the EHBA(Cr/sup V/) complex caused by a different chemical structure of the used organic acid.