Excited-state X-band EPR in a molecular cluster nanomagnet -: art. no. 212401

The X-band excited-state electron paramagnetic resonance (EPR) spectra of Mn-12-acetate nanomagnet crystals has been measured. Three lines belonging to the m = -1 <-> 0 transition at H-C = 600 G and to the m = 0 <-> -1 and m = -2 <-> -1 high-field transitions at 7800 and 9200 G, respectively, were detected below 50 K in agreement with the energy level scheme obtained from high-field EPR. The lines are rather broad. T-2 is shorter than 30 ns and T1T2< 10(-15) s(2). Similarly broad excited-state EPR spectra were also observed in a Fe(8) single crystal.