XUV-laser spectroscopy of HD at 92-98 nm

Sub-Doppler excitation spectra of HD have been recorded in the range 92--98 nm with the use of a narrow-band and tunable extreme ultraviolet laser in combination with a molecular beam. Frequencies of 147 transitions to the {ital B} {sup 1}{Sigma}{sub {ital u}}{sup +}, {ital C} {sup 1}{Pi}{sub {ital u}}, and {ital EF} {sup 1}{Sigma}{sub {ital g}}{sup +} states have been calibrated with an average absolute accuracy of 0.035 cm{sup {minus}1}. The data have been analyzed in the framework of a semiempirical deperturbation model involving mutual couplings between nearby lying levels of the {ital B} {sup 1}{Sigma}{sub {ital u}}{sup +} and {ital C} {sup 1}{Pi}{sub {ital u}} states. Also, symmetry-breaking effects, i.e., interactions with {ital EF} {sup 1}{Sigma}{sub {ital g}}{sup +} gerade states, were inferred from the data.