Flame sampling photoionization mass spectrometry of CH3PO2 and CH3OPO2

Laser photoionization mass spectrometry has provided the first detection of the isolated dioxophosphoranes, CH3PO2 and CH3OPO2. These molecules are found to be key intermediates in the combustion of dimethyl methylphosphonate (DMMP). Near-threshold photoionization efficiency curves, produced with a tunable vacuum ultraviolet (VUV) laser light source, yield ionization potentials of 9.24 ± 0.01 and 8.97 ± 0.02 eV for CH3PO2 and CH3OPO2, respectively. A newly developed flame-sampling laser-ionization mass spectrometer provided measurements of concentration profiles of these species throughout the flame zone of a premixed, low pressure hydrogen/oxygen/argon flame, seeded with DMMP.