AbstractThe recently developed FT LMMS with an external ion source has been applied to selected organic molecules. Some aspects of the ion formation processes from solids under focused laser irradiation at 266 nm were investigated. Specifically, the effect of laser energy and the time profile of ion production were studied. First, the generation of intact cations, fragments and thermal decomposition products from a quaternary ammonium salt were evaluated at distinct times after the laser pulse. The mass spectra of phenol red in its neutral and salt form were recorded under different conditions with respect to laser irradiation power density conditions and ion formation after the laser pulse. The results allow the refinement of previous concepts about ionization in LMMS.