Absorption spectra of H2O and D2O molecules in the vacuum-ultraviolet region

The absorption spectra of H 2 O and D 2 O molecules have been studied in the region from 1130 to 500 AA using a 1.3 GeV electron synchrotron as a background source and a vacuum-ultraviolet (VUV) spectrograph equipped with a 50 cm grating. Many vibrational bands associated with the 'CD' Rydberg series are observed in the 1130-980 AA region and are classified into three (CC'D) Rydberg series accompanied by vibrationally excited states. A number of bands in the 980-800 AA region are assigned to vibrational progressions of the 3a 1 to nd Rydberg series, and the bands in the 800-650 AA region to the vibrational progression corresponding to the 1b 2 to 4sa 1 transition. A continuum lying in the 1000-800 AA region is attributed to the 1b 2 to 3sa 1 transition.