Excitation and Negative Ions in H2O

By combining the trapped-electron method with the study of negative ions and positive ions, it is possible to obtain data which can be used for construction of an approximate potential energy diagram of molecules. The experimental methods used are described and the H2O molecule is discussed. The negative ion current peaks at 6.5±0.1 and 8.8±0.1 ev. Kinetic energy measurements on the negative ions show that the latter peak is associated with the same state at infinite separation as the first peak. The inelastic loss processes are essentially in agreement with optical absorption experiments. An inelastic process with a threshold at about 3.4 ev is observed.