laser ionisation spectroscopy resonance ionisation spectroscopy resonance ionisation spectrometry resonance ionization spectroscopy resonance ionization spectrometry resonance enhanced ionization spectroscopy resonance enhanced ionisation spectroscopy reonance enhanced ionization spectrometry CHMO:0000463 RIS resonance enhanced ionization spectrometry resonance enhanced ionisation spectrometry Spectroscopy where a sample is illuminated with resonant laser light (using a laser which is tuned to match an electronic transition within the sample) and photoexcitation is used to promote an atom or molecule above its ionisation potential to create an ion.