2D EPR INVESTIGATION OF ENDOHEDRAL LA-AT-C-82 IN SOLUTION

The analysis of a two-dimensional EPR spectrum gives direct evidence for a dominant nuclear quadrupole interaction at the site of the encapsulated La3+ ion. From the observed nuclear spin transition rates we deduce eQV(zz)/[I(2I - 1)h] approximate to 0.5(3) MHz, assuming that the correlation time of the electric field gradient axes is determined by molecular reorientation of the molecule in solution. The non-vanishing value of the quadrupole interaction is further proof for an off-center position of the metal ion.