Near-Threshold Low Rydberg Depletion Spectroscopy of H₂, D₂, and HD

Using high-resolution depletion spectroscopy, we have experimentally studied the physics of near-threshold low Rydberg states of all three stable isotopic variants of molecular hydrogen. The experiments were required to calibrate the absolute wavelength, including several transitions from the EF (v=0) and EF (v=6 or v=9) to the same low-n Rydberg states. The measurements have been performed for several initial rotational levels in all three stable isotopic variants. Transitions to very high vibrational levels of the B, B', and C states have been measured with accuracy 0.002cm¹. The pulsed amplifier perturbations were also measured by optical heterodyne methods.