A STUDY OF DESTRUCTION OF HIGHLY EXCITED MOLECULAR IONS PRODUCED IN THE EXTREME-ULTRAVIOLET REGION

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As well as the study of the multiply excited ionic states, i.e., the photoionization satellites, the study of molecular highly excited states excited by the photoabsorption of the energy above ca. 25 eV is quite improtant from the view point of the chemistry of highly excited molecules accompanying the electron correlation effect. The purpose of the present investigation has been to delope the spectroscopic method to identify and to observe the production and decay processes of such molecular highly excited states through the coincident measurments of the fragment photoions with the fluorescence from electronically excited neutral fragments. As shown below the purpose of the present investagation has been well accomplished.The present investigation has been carried out through the constructioin of the above mentioned experimental apparatus, nemely, a coincidence spectrometer, which is composed of a pulsed electromagnetic gas nozzle, a fluorescence detector, and a time-of-flight mass an … More alyzer and installed in a presently available highly evacuated vacuum chamber for collision of gas phase molecules with an extreme-ultraviolet photon beam. By developing, tuning, and using this apparatus, the investigation of entitled study has been performed for the tyipical diatomic molecules, such as hydrogen and nitrogen, by employing the monochromatized synchortron radiation at the Photon Factroy, the National Laboratory for High Energy Physics, Tsukuba.As for the results for nitrogen, the highly excited ions dissociating into a fragment ion (N^+) and an electronically excited neutral fragment (N^<**>) has been shown to correspond to the ions produced by the emission of electron from an inner valence orbital, with which almost no information was obtained previously. The detailed measurements of coincinent excitation funtin of fragment ions with fluorescence photons as a function of excitation photon energy have been performed. Also it has been successfully performed to reveal the production of ionic states with various symmetries the angular dependent coinicidence spectroscopy with respect to the polarization axis of synchrotron radiation. These have been the clear evidence showing the strong correlation between the one-electron ionic states and the multiply excited neutral molecules. Based on this rsult, the measurement of dispersed fluorescnce has been perfomed. It has been shown that a significant contribution of the fluorescence from ionic fragments is involved and that a certain molecular ionic state correlates to a certain fragment pair.As for the results for hydrogen, the coincidence spectra have shown that the one-electron ionic states with another one-electron excitetaion dissociate into a H^+ and a H^<**>, for which a detailed investigation has been performed by the measurements two dimensional coincidence spectroscopy. Further detailed information has been obtaine by the kinetic energy analysis of fragment ions using an electrostatic analyzer. Less