Mass Selective Resonant Two Photon Ionization (R2PI) Spectroscopy

After neutral laser desorption and jet cooling, we employ various lasers to ionize and detect the molecule in a reflectron time of flight mass spectrometer (reTOF MS). If we use resonant two photon ionization (R2PI, sometimes referred to as resonance enhanced multi-photon ionization or REMPI), the first photon resonantly excites the molecule while a second photon ionizes the excited molecule. By varying the excitation wavelength while monitoring specific mass peaks we obtain mass selected, vibrationally resolved spectra in the excited state.