The spectrum of photoionization efficiency (PIE) of S2O2 was measured in th
e spectral range 105-130 nm by means of a discharge flow and a photoionizat
ion mass spectrometer coupled to a synchrotron as a radiation source. S2O2
was generated from self reaction of SO radicals, SO+SO-->S2O2, in a gaseous
flow system. SO radicals were produced on reacting O atoms with CS2 and OC
S, The ionization energy (IE) of S2O2 was determined to be (9.93+/-0.02) eV
. (C) 1999 American Institute of Physics. [S0021-9606(99)02401-0].