Relaxation oscillations during the laser-induced spin state transition of a [Fe(PM-BiA)2(NCS)2] complex

Abstract

We performed an optical pump-probe experiment to monitor the laser-induced spin state transition of [Fe(PM-BiA)${}_{2}$(NCS)${}_{2}$] spin crossover microcrystallites. The sample is illuminated by a continuous-wave pump laser centered at \ensuremath{\lambda} $=$ 976 nm that switches the compound from the low-spin to the high-spin state. When the pump laser is switched on or off, and above a given power threshold, the diffuse reflectivity of the sample increases or decreases, respectively, and presents characteristic damped oscillations that are not due to laser-induced excited spin state trapping. We propose a shell-core model that, due to the laser-induced heating and spin state transition of the microcrystallites, accounts very well for the reported observations.