Theoretical studies on core-level spectroscopy: Dynamical effects
Molecular Physics seminar
Monday 17 December 2012
to 11:00 at
Osamu Takahashi (Hiroshima University )
Core-level spectroscopy using X-rays is an important tool to probe electronic states in molecules and materials and widely used in various fields of science; physics, chemistry, biology, and also geology. Recently, double core hole (DCH) spectroscopy from the K-shell is one of hot topics. DCH spectroscopy from other shells have been investigated extensively from 70’s to 80’s. For the K-shell DCH study, theoretical poineering works have been performed by Cederbaum et al, and followed by Ågren et al. Although experimental detections of DCH states were very difficult due to small cross sections, several experimental results were reported recently with experimental improvements of synchrotron radiation and emergence of X-ray free electron laser. Stimulating such experimental progress, theoretical studies have been revived again.
In this talk, I introduce some recent results of ionization potential (IP) for K-Shell single core hole (SCH) creation and double ionization potential (DIP) for K-Shell double core hole creation of XHm-YHn (X, Y = C, N, O, F, m,n=0-3) and C60 within the framework of density functional theory (DFT). For these molecules, we estimated the relaxation energies (a measure of the electron density flow to the core-hole site) and the interatomic relaxation energies (a measure of the electron density flow to the two core-hole sites) from the calculated IPs and DIPs. For XHm-YHn, we find that the interatomic relaxation energy for the DCH states having two holes at X and Y atoms decreases with increasing bond order between X and Y. For DCH states having two holes at two carbon atoms in C60, we find that the interatomic relaxation energy decreases with increasing hole-hole distance. Finally, I talk about the dynamical effects on the core-hole and double-core-hole states of a single water molecule.