Nuclear motion and dissociation dynamics of core-excited molecules

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Nuclear motion and dissociation dynamics of core-excited molecules have been investigated using monochromatic soft X-rays obtained from the high-resolution monchromators installed in the synchrotron radiation facilities. Major results can be summarized as follows.(1) Vivrational structure have been resolved in the O 1s excitation spectrum of H_2O molecules for the first time. It was found that the O 1s^<-1> 2b_2 excited state has a potential minimum and that H_2^+ ion formation after the Auger decay increases with the increase in energy stored in the O 1s^<-1> 2b_2 excited state. It was also found that the nuclear motion of the Auger final 1b_2^<-1> state can be controlled significantly by tuning the excitation energy within the 1s→2b_2 resonance.(2) The doubly-degenerate core-excited II state of CO_2 splits into two due to static Renner-Teller effect. The linear and bent geometries for the B_1 and A_1 Renner-Teller pair states have been probed directly and separately, using the triple-ion-coincidence momentum imaging technique and focusing on the dependence of the measured quantities on the polarization of the incident light. Furthermore dynamical coupling between B_1 and A_1 state were investigated using symmetry-resolved, vibrationally-resolved excitation spectra.(3) The out-of-plane nuclear motion of the BF_3 planar molecule in D_<3h> symmetry induced via B 1s to 2a_2" excitation has been probed by angle-resolved ion yield spectroscopy, resonant Auger electron spectroscopy and quadruple-ion coincidence momentum imaging technique.(4) The asymmetric nuclear motion of the CF_4 and SiF_4 molecule in T_d symmetry induced via F 1s to 2t_2" excitation has been investigated by measuring the anisotropic fragmentation of the F+ ion and the Doppler-shifted anistoropic Auger emission from thedeparting F atom produced via the ultrafast molecular fragmentation of the molecule after the core-excitation but before the Auger decay.