We describe a method for performing time-resolved X-ray crystallographic
experiments based on the Hadamard transform, in which time resolution is defined
by the underlying periodicity of the probe pulse sequence, and signal/noise is
greatly improved over that for the fastest pump-probe experiments depending on a
single pulse. This approach should be applicable on standard synchrotron
beamlines and will enable high-resolution measurements of protein and
small-molecule structural dynamics. It is also applicable to other time-resolved
measurements where a probe can be encoded, such as pump-probe spectroscopy.
