SUB-DOPPLER LASER SPECTROSCOPY OF H-2 AND D-2 IN THE RANGE 91-98 NM

The absorption spectra of hydrogen and deuterium have been measured in the range 91-98 nm. A narrowband extreme ultraviolet laser source is employed in combination with a molecular beam, allowing for sub-Doppler resolution and yielding linewidths of 0.23 cm(-1). Transition frequencies of 291 lines of the Lyman and Werner bands are determined with an average absolute accuracy of 0.03 cm(-1). The data are analyzed in a semi-empirical perturbation model, involving heterogeneous couplings between nearby lying levels of B-1 Sigma(u)(+) and (CIIu)-I-1 states. This model is found to be accurate on the level of accuracy of the data obtained.