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 H₂ and D₂ are measured directly and absolutely at intensities up to the ionization threshold of ∼10¹⁴W/cm².   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.