Excited-stateX-band EPR in a molecular cluster nanomagnet

Abstract
The X-band excited-state electron paramagnetic resonance (EPR) spectra of Mn12-acetate nanomagnet crystals has been measured. Three lines belonging to the m=10 transition at HC=600G and to the m=01 and m=21 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. T2 is shorter than 30 ns and T1T2<1015s2. Similarly broad excited-state EPR spectra were also observed in a Fe(8) single crystal.