抄録
A vacuum ultraviolet monochromator and a quadrupole mass spectrometer have been combined with the differential pumping systems, since hydrogen, helium and argon gases were used as the carrier gas for the photon source. The photoionization efficiency curves were observed by the hydrogen many-line spectrum. The photoionization efficiency curves for the parent and the fragment ions of (CH3)2 CO have been measured with the photon band width of 0.9Å. For the parent ion, autoionization for super-excited states was first observed in the threshold region of the photoionization.