Ionization Quantum Yields and Absorption Coefficients of Selected Compounds at 58.4 and 73.6-74.4 nm

The ionization quantum yields and I he extinction coefficients of a number of compounds have been determined at the wavelengths of the helium (58.4 nm) and neon (73.6-74.4 nm) resonance lamps. These are lamps with thin aluminum windows (100-200 nm) which we inserted in a glass cell backed by a second cell. Both cells are provided with parallel plate electrodes and separated from each other by an aluminum window. The ionization quantum yields are based on ionization efficiency of argon which is unity. Hydrogen, which has an ionization quantum yield of 0.94 and 1.00 at 73.6-74.4 and 58.4 nm respectively, was used as a secondary standard because it yielded better defined saturation ion current plateaus. The extinction coefficients were determined in both a double cell and a single cell arrangement. The agreement between the two measurements was excellent. In general an inert diluent was added to the gas of interest in order to improve the plateau of the saturation ion current. These results are compared with the literature values, which were mainly determined in windowless systems with monochromators.