Core-excitation Processes Research Articles

High Resolution Soft X-Ray Spectroscopies with the Dragon Beamline

Novel spectral features and new information regarding core-excitation processes are revealed in the photoabsorption and photoemission experiments performed with a newly constructed synchrotron radiation beamline. This beamline, dubbed Dragon, has an unprecendented resolving power and superior transmission in the soft x-ray region. Several experimental results on gas phase, solid and biological systems are presented to exemplify the scientific applications of high resolution soft x-ray spectrocopies. The possible application of photoabsorption spectroscopy as a tool for chemical analysis is also discussed and a few examples are given.

Discrete variational Xα studies of core excitation, photoemission, and inverse photoemission for CO and NiCO clusters

The discrete variational (DV)-Xα method has been applied to CO and NiCO clusters to investigate core excitation, photoemission, and inverse photoemission spectroscopy. The transition state calculations demonstrate several important features of these excitation processes. A significant difference in the appearance of the screening effect due to the core hole is observed between photoemission and core excitation processes. The core excitation shows a greater difference in shifts between the C 1s and the O 1s electron excitations and also a stronger dependence on the bond lengths for Ni–C and C–O than those found for the ionization process. The intensity of the core excitation is briefly described in terms of the calculated dipole transition probability.

Core excitations in (d,p) reactions including transitions to continuum levels

Effects of core excitations in (d, p) reactions are investigated for 12C(d, p) 13C ∗ reactions in the CCBA framework, where couplings of channels are considered for the ground and first-excited levels of 12C in the initial state and for the bound 1 2 + and 5 2 + levels and low-lying continuum levels of 13C in the final state, where a discretization is introduced for the continuum region. In the transitions to the continuum levels, matrix elements are calculated by the use of scattering-state wave functions for the final neutron. Theoretical cross sections and vector analyzing powers are compared with experimental data, where significant contributions of core-excitation processes are identified, particularly in the transition to the 5 2 + II level of 13C. Spectra of emitted protons are calculated and compared with the measured ones. Adequate agreement between theory and experiment is found throughout the present investigation.

T>giant resonance inNd142via the reactionNd142(e,e′p)

The reaction $^{142}\mathrm{Nd}(e,{e}^{\ensuremath{'}}p)^{141}\mathrm{Pr}$ has been used to study the ${T}_{>}$ giant resonance in $^{142}\mathrm{Nd}$. Cross sections for the $^{142}\mathrm{Nd}(\ensuremath{\gamma},p)^{141}\mathrm{Pr}$ and $^{142}\mathrm{Nd}(\ensuremath{\gamma},{p}_{0}+{p}_{1})^{141}\mathrm{Pr}$ reactions were measured for excitation energies from 15.9 to 26.0 MeV. These cross sections are compared with previous $^{141}\mathrm{Pr}(p,{\ensuremath{\gamma}}_{0})^{142}\mathrm{Nd}$ data. The angular distributions for the larger resonances at 17.3, 19.7, and 22.9 MeV were measured. Analysis indicates that the 22.9-MeV state has about a 13% $E2$ component. The decay proton spectra from the 19.7- and 22.9-MeV resonances were analyzed with a schematic shell model and indicates that the core excitation process is dominant in these isobaric analog resonances. The measured ($\ensuremath{\gamma},p$) cross section together with the ($\ensuremath{\gamma},n$) cross section is found to be fairly consistent with the predictions of isospin splitting theory.NUCLEAR REACTIONS $^{142}\mathrm{Nd}(e,{e}^{\ensuremath{'}}p)$, $E=15.9\ensuremath{-}26$ MeV; measured $\ensuremath{\sigma}(E;{E}_{p})$; deduced $\ensuremath{\sigma}(\ensuremath{\gamma},p)$, $\ensuremath{\sigma}(\ensuremath{\gamma},{p}_{0}+{p}_{1})$. $E=18.0, 19.8, 20.8, 22.9, 23.9$ MeV: measured $\ensuremath{\sigma}({E}_{p},\ensuremath{\theta})$. $^{142}\mathrm{Nd}$ deduced isobaric analog resonances. Enriched target.