Frequency domain magnetic resonance spectroscopy on [Mn12]- and [Mn9]:: Zero-field splittings and lineshape analysis

The zero-field splitting paramenters of two non-integer spin state single molecule magnets were determined using frequency domain magnetic resonance spectroscopy: D = -0.454 +/- 0.004 cm(-1), B-4(0) = (+1.01 +/- 0.05) X 10(-5) cm(-1) for [Mn-12](-), and D = -0.247 +/- 0.005 cm(-1), B-4(0) =(+4.6 +/- 0.1) X 10(-6) cm(-1) for [Mn-9], leading to a Gaussian lineshape. Interestingly, the resonance line is homogeneously broadened in the case of [Mn-12](-), which is one of the few examples in single molecule magnetism. This means that the linewidth is determined by the excited spin state lifetime, which can be calculated to be 50-58 ps depending on the temperature. (c) 2005 Elsevier Ltd. All rights reserved.