Laser induced spin state transition: Spectral and temporal evolution

Photo-switching dynamic from the low-spin state to the high-spin state after a nanosecond laser pulse excitation. At 150 K, we have recorded the evolution of the energy threshold versus the wavelength and the kinetic of formation and relaxation of the spin state phase transition induced by a single laser pulse in the [ Fe ( PM-BiA ) 2 ( NCS ) 2 ] compound. We demonstrate that different absorption bands of the complexes can drive the phase transition. The saturation-energy and the threshold-energy of the laser pulses are not directly related to the absorption cross-section of the sample. Both the switching and the relaxation kinetics are well fitted using two different time-constants. The switching lasts about 50 μs. The relaxation time-constants are independent of the used excitation-wavelength.