  We report with single particle simulations that longitudinal chromatism, a
commonly occuring spatio-temporal coupling in ultrashort laser pulses, can have
a significant influence in the longitudinal acceleration of electrons via
high-power, tightly-focused radially polarized laser beams. This effect can be
advantageous, and even more-so when combined with small values of temporal
chirp. However, the effect can also be highly destructive when the magnitude
and sign of the longitudinal chromatism is not ideal, even at very small
magnitudes. This motivates the characterization and understanding of the
driving laser pulses, and further study of the influence of similar low-order
spatial-temporal couplings on such acceleration.
