Nanosecond time-resolved crystallography of photo-induced species: case study and instrument development for high-resolution excited-state single-crystal structure determination
Abstract
This work describes one of the first stages in the development of time-resolved photo-induced small-molecule single-crystal diffraction, whereby transient electron density perturbations, with lifetimes down to the nanosecond level, can be resolved at the atomic level. Knowledge of such ephemeral electronic effects is likely to yield key information regarding the origins of certain important physical properties, e.g. luminescent and non-linear optical effects, since it will allow the dynamics of electron density to be identified and quantified, and it is this that underpins such phenomena in a given molecule. The experimental methodology employs phase-locking pump–probe techniques such that the inherent time-structure of a synchrotron X-ray beam (nanoseconds) is harnessed and time-gated in-phase with a femtosecond laser. The resultant beams, made coincident on the crystal in a periodic manner, and a diffraction pattern are recorded as
a function of the Bragg angle, θ. Such technology is based upon the pioneering work carried out in sub-nanosecond time-resolved