Precision measurements and test of molecular theory in highly-excited vibrational states of H2 (v=11)
Abstract
Accurate EF1+g-X1+g transition energies in molecular hydrogen were determined for transitions originating from levels with highly-excited vibrational quantum number, v=11, in the ground electronic state. Doppler-free two-photon spectroscopy was applied on vibrationally excited H2*, produced via the photodissociation of H2S, yielding transition frequencies with accuracies of 45 MHz or 0.0015 cm-1. An important improvement is the enhanced detection efficiency by resonant excitation to autoionizing 7pπ electronic Rydberg states, resulting in narrow transitions due to reduced ac-Stark effects. Using known EF level energies, the level energies of X(v=11, J=1,3-5) states are derived with accuracies of typically 0.002 cm-1. These experimental values are in excellent agreement with, and are more accurate than the results obtained from the most advanced ab initio molecular theory calculations including relativistic and QED contributions.