Highly sensitive in-situ Analysis of Gasphase Molecules by Laser Mass Spectroscopy


REMPI, a fast and selective ion source for mass spectrometry

Resonance-enhanced multiphoton-ionization (REMPI) stands out due to extraordinary selectivity if the first absorption step takes place at a wavelength which is resonant for one, but non-resonant for the other species in a mixture. Since REMPI is a ionisation process, the so-produced ions may be selected in a mass spectrometer. Time-of-flight mass spectrometers (TOF-MS) are here of particular advantage. REMPI with all its variations is an optimal means to perform electronic spectroscopy and to study chemical and photochemical processes in the rarefied gas phase. Its extraordinary selectivity and sensitivity additionally makes REMPI combined with TOF-MS to a powerful analytical tool for traces of compounds in highly complex gas mixtures. The combination of REMPI with pulsed lasers and TOF-MS has the further advantage of high speed of measurement. Complete mass spectra may be taken with kHz repetition rate. 

Application to technical combustion processes

Together with partners of the automobile and laser industry we develop and apply REMPI-TOF-MS and related techniques to monitor and study emissions from combustion engines. Problems to tackle are:

  • Small concentrations (down to ppb and sub-ppb) 
  • Fast and strong fluctuations of concentration
  • Dynamic processes in the combustion chamber 
  • Fast chemical processes in catalytic converters
  • Traces of motor oil in the exhaust gases
  • Dynamic motor oil consumption diagnostics with 100 ms-cycle
  • Crank angle resolved and in-cylinder chemical analysis
  • Synchronous detection of different trace compounds
  • Monitoring of PAH´s, Aldehydes, CO, CO2, NO, NO2, N2O, NH3, SO2, H2S and many more

Project Funding

  • Bayerische Forschungsstiftung (BFS)
  • Bundesministerium für Bildung und Forschung (BMBF)
  • Fördervereinigung für Verbrennungskraftmaschinen (FVV)