Absolute measurement of the ultrafast nonlinear electronic and rovibrational response in H${}_2$ and D${}_2$

The electronic, rotational, and vibrational components of the ultrafast optical nonlinearity in H${}_2$ and D${}_2$ are measured directly and absolutely at intensities up to the ionization threshold of $\sim$10${}^{14}$ W/cm${}^2$. As the most basic nonlinear interactions of the simplest molecules exposed to high fields, these results constitute a benchmark for high field laser-matter theory and simulation.