Mass spectrometer with photoionization ion source method and system

摘要

Method for producing ions for mass spectrometry analysis, including introducing vaporized sample compounds behind a supersonic nozzle and expanding the sample compounds with a carrier gas from the supersonic nozzle into a supersonic nozzle vacuum chamber proximate thereto for vibrationally cooling the sample compounds prior to their ionization. Sample compounds are ionized by either illumination with vacuum ultra-violet photons produced by a continuously operated vacuum ultra-violet photon source or by electrons produced in a fly-through electron ionization ion source; and the ions are transferred to a mass analyzer mounted in a mass analyzer vacuum chamber to obtain mass spectra from vibrationally cold molecules. A quadrupole mass analyzer mounted may be used to obtain mass spectra with dominant molecular ions and fragment ion intensities below 3% of the molecular ion for hydrocarbons. Carrier gas flow rate may exceed 20 ml/min for vibrationally cooling the sample compounds prior to their ionization.