Fig. 5. Iodine oxide particles (IOP) pyrolysis experiments at 11.6 eV.

The particles are grown along the flow tube, and the carrier gas and particles are passed through a 1-cm diameter resistively heated filament coil just before sampling to detect evaporation products. At a lower filament current of I = 1.7 A (lower temperature at the sampling point), the spectrum obtained at 30 Torr with 2% water mixing ratio resembles other broadband photolysis (BBP) spectra in Fig. 2. When the current through the coil is higher (3.8 A), the spectrum changes (red line) as a result of particle evaporation: the higher masses disappear, the I₂ signal increases and new masses show up at m/z = 144 (HOI⁺) and m/z = 176 (HOIO₂⁺). When water is not added actively to the flow, the oxyacid ion signals decrease drastically, but still some detectable signals remain due to release of water from the inner walls of the experiment. The vertical black lines indicate the position of the oxide and oxyacids in the m/z axis: from left to right: I, IO, HOI, OIO, HOIO, HOIO₂, HIO₄, I₂, I₂O, I₂O₂, I₂O₃, I₂O₄, I₂O₅, HI₂O₅, I₃O₅, I₃O₆, I₃O₇. Time-of-flight mass spectrum (ToF-MS) signal in arbitrary units.