Quantitative spectroscopic and theoretical study of the optical absorption spectra of H ₂O, HOD, and D ₂O in the 125-145 nm region

Synchrotron radiation was used to determine the room temperature absorption spectra of water and its isotopomers D ₂O and HOD in absolute cross section units in the 125 to 145 nm wavelength region. The cross sections at a temperature of 300K were calculated by applying a Monte Carlo sampling over the initial rotational states of the molecules. Two more resonances were found at low energy in the case of HOD. The width of the resonances of 0.04 eV is the result of overlapping and narrower resonances in the spectra of molecules differing in rotational ground state.