One-color resonant and nonresonant ionization studies of Si2N and Si2O have been performed using a pulsed laser vaporization cluster source in conjunction with a time-of-flight mass spectrometer. The ionization potential of Si2N is established as less than 6.4 eV, while the ionization potential of Si2O is bracketed between 6.4 and 7.9 eV. The experimentally established ionization potential for Si2N is confirmed by detailed molecular electronic structure calculations which indicate an adiabatic as well as vertical ionization potential of 6.2 +/- 0.05 eV and a close similarity between neutral Si2N and ionic Si2N+. Similar detailed calculations lead to a best estimate of an adiabatic ionization energy of 7.42 +/- 0.04 eV and a vertical ionization energy of 7.66 +/- 0.04 eV for Si2O.