Relaxation dynamics of Cr(acac)3 probed by ultrafast infrared spectroscopy

Ultrafast infrared spectroscopy is used to probe the dynamics of Cr(acac)(3) upon ligand field (400 nm) and charge transfer state (345 nm) excitation. At both pump wavelengths, the ground state absorption bands are strongly bleached at zero delay, and new broad transient absorption bands appear red shifted from the bleached bands. Recovery of ground state bleach is dominated by a fast time constant (15 ps), while a small percentage recovers within 760-900 ps. Despite the extensive studies on Cr(acac)(3) photophysics, the fast recovery of the ground state as a major channel is reported here for the first time. As a general result, the present communication emphasizes the great value of ultrafast infrared spectroscopy in inorganic photophysics.