The Balmer-β emission from the H and the D atoms has been observed by electron impact on the mixtures of H2O and D2O with several mixing ratios at selected incident electron energies over the range of 22-100 eV. Intensity ratios of the emission have been estimated from computer simulation of the emission spectra on each combination of the mixing ratios and the electron energies. Analyzing the intensity ratios, the H(n=4)/D(n=4) branching ratio in the dissociation of pure HOD has been estimated for the first time to be about 1.8 below the second threshold (∼26 eV) of the Balmer-β emission, where it is about 1.5 over 40-100 eV. It has also been found that the ratios of the cross section of the H Balmer emission from H2O to the D Balmer emission from D2O are equal to those of HOD, and the ratios of the D Balmer emission from D2O to that from HOD are constant and about two over 22-100 eV.
All Science Journal Classification (ASJC) codes