MODIFICATION OF AN MS9 MASS-SPECTROMETER FOR DOUBLE-CHARGE-TRANSFER SPECTROSCOPY

An MS9 mass spectrometer has been modified for double-charge-transfer spectroscopy. The translational-energy losses when fast-moving OH+ ions undergo charge-inversion reactions with thermal molecules contained in a collision-gas cell located at the intermediate focal point have been measured. From the experimental data, the double ionization energies of CF4 and CCl4 have been determined and are found to agree with values determined previously using a reversed-geometry ZAB-2F spectrometer. An important component fitted to the modified spectrometer is a heated reservoir which is coupled by a heated inlet line to the collision-gas cell. This allows molecules of low vapour pressure liquids and certain solids to be introduced into the cell. Carbon tetrabromide, a solid at room temperature, has been investigated with this system and its double ionization energy determined to be 27.9 ± 0.5 eV. This agrees with a value determined previously by Auger electron spectroscopy. The results obtained so far show the potential of the modified MS9 spectrometer for double-charge-transfer experiments especially when molecules of samples having low vapour pressures are to be studied. © 1990.