FREE ION YIELDS IN LIQUIDS EXPOSED TO SYNCHROTRON X-RAYS

A synchrotron light source was utilized to measure the yields of ions for exposure of nonpolar liquids to monochromatic X-rays as a function of energy (1.8-4.0 keV). For n-hexane, 2,2,4-trimethylpentane, and 2,2,4,4-tetramethylpentane, the yields per 100 eV (G values) decreases monotonically with decreasing photon energy, that is, as the rate of energy loss of the photoelectron increases. The yields increase with an increase in the applied electric field. The results are consistent with a track model. For liquid CCl4, sharp resonances are observed at energies just below the K edge of chlorine. These are "negative" peaks, that is, dips in the ion yield associated with excitation of a 1s electron in chlorine to unoccupied orbitals.