Study of Spin-forbidden Ionization and Excitation via Inner-shell Excitation

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The spin-forbidden transitions become observable in addition to spin-allowed multiplets in the soft X-ray photoelectron spectra and soft X-ray emission spectra by tuning the photon energy to the inner-shell excitation as an intermediate state. In this research, resonant spectroscopy of photoelectron and photon emission was applied to reveal spin-forbidden valence ionized states and valence excited states. Theoretical and experimental approaches for such resonant spectroscopy were developed. Spin multiplets are produced due to exchange interaction ; therefore, multiplet interaction in open-shell molecules was especially studied in detail.In the theoretical approaches, an ab initio R-matrix/Multi Quantum Defect Theory (MQDT) method was newly developed to analyze systematically both the bound state below the ionization threshold and the continuum state above the threshold. This R-matrix/MQDT approach was applied to open-shell molecules such as NO and O_2. We successfully distinguished between characteristics of inner-shell excitation and of individual molecule. The theoretical approach to treat core-valence exchange interaction reasonably has been established in this work.In the experimental approaches, a new-type and next-generation soft X-ray emission spectrometer was developed. The present energy resolution was about 4,500. This resolution is the best in the world and is much higher than the previous best resolution. The CCD detection system was improved to detect soft X-rays emitted via C, N and O is excitation. The transmission grating system was also designed to detect soft X-rays emitted via C, N and O 1s excitation. The experimental approach to treat spin-forbidden valence excitation has been established in this work. In addition, it is revealed with a newly-developed cluster photoelectron apparatus that forbidden bands in a single molecular system are observable after molecular cluster formation.