Scheme 1. Kerr-Gated Time-Resolved Resonant Raman Experiment of P10 (Structure Upper Left).

The laser pump pulse (400 nm) generates photoexcited states that can be subsequently interrogated by the probe pulse (630 nm) which is delayed with respect to the pump (Δt). The wavelength of this probe pulse was selected to be resonant with an electronic transition associated with a transient species observed in the transient absorption spectra of P10. The probe pulse generates both Raman scatter and photoluminescence (PL). An ∼2 ps duration 800 nm high-energy laser pulse induced a transient optical anisotropy which lasts for approximately the duration of the gating pulse in the CS₂ Kerr medium. During this period the gate is “opened”, and the polarization of the incident linearly polarized light is rotated by 90° with respect to its original orientation and passed through the crossed exit polarizer into the spectrometer while the unrotated light is rejected. Raman scattering is a fast process that occurs on a subpicosecond time scale. By synchronizing the timing of the Raman probe laser pulse with the gate pulse, it is possible to selectively transmit Raman scattered photons while rejecting the majority of the much longer lived (ns or greater) PL.