Patent ID: 7521671

Claim:
A laser ionization mass spectrometer comprising pulsed gas ejecting means, a laser beam irradiation system, repeller and extraction electrodes and mass analyzing means characterized in that said pulsed gas ejecting means is provided with a valve for ejecting carrier gas containing sample molecules into a vacuum chamber in pulse mode, that said laser beam irradiation system irradiates laser beam to said carrier gas ejected into said vacuum chamber for selective photo reaction of said sample molecules in said carrier gas ejected into said vacuum chamber, that said repeller and extraction electrodes are arranged within said vacuum chamber and generate an electric field for extracting sample molecules formed by said photo reaction, that said mass analyzing means analyzes mass of sample molecular ions extracted by said repeller and extraction electrodes, that a valve of said pulsed gas ejecting means is set so that said pulsed gas has pulse length shorter than a distance from an ejecting position to said laser beam irradiation point to said carrier gas and that said laser beam irradiation system is set so as to irradiate laser beam to said carrier gas near a position whereat a leading portion gas of said pulsed gas translating in said vacuum chamber, i.e. a gas ejected before full opening of said valve, is overtaken by a faster flat portion gas, i.e. a gas ejected during full open of said valve.