MAGNETIC-FIELD AND MAGNETIC ISOTOPE EFFECTS UPON REACTIONS OF HEAVY ATOM-CENTERED RADICALS

We present our recent studies on magnetic field effects (MFEs) observe d in reactions of heavy atom-centered radicals such as Si-,P-, Ge-, an d Sn-radicals with a ns-laser photolysis technique under magnetic fiel ds of 0 - 10 T. Although the MFES of heavy atom-centered radicals are much smaller than those of C-radicals due to the spin-orbit interactio n of heavy atoms, we have found appreciable MFEs in many reactions of such heavy atom-centered radicals. Comparing the MFES of C-radicals wi th those of heavy atom-centered ones, we have explained the MFEs of he avy atom-centered radicals in terms of the Delta g and relaxation mech anisms. We have found that the separation between the MFES due to the Delta g mechanism and those due to the relaxation one is possible with the enhancement of spin relaxation by the addition of a paramagnetic ion. We have also tried to enrich magnetic isotopes of heavy atoms wit h the magnetic isotope effect (MIL), using the reactions which show fa irly large MFES. Recently, we have succeeded in enriching Ge-73. This is the heaviest isotope which has so far been enriched with the MIE fr om samples of natural abundance.