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

We present our recent studies on magnetic field effects (MFEs) observed in reactions of heavy atom-centered radicals such as Si-,P-, Ge-, and Sn-radicals with a ns-laser photolysis technique under magnetic fields 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 interaction of heavy atoms, we have found appreciable MFEs in many reactions of such heavy atom-centered radicals. Comparing the MFES of C-radicals with those of heavy atom-centered ones, we have explained the MFEs of heavy atom-centered radicals in terms of the Delta g and relaxation mechanisms. 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 with the magnetic isotope effect (MIL), using the reactions which show fairly large MFES. Recently, we have succeeded in enriching Ge-73. This is the heaviest isotope which has so far been enriched with the MIE from samples of natural abundance.