Search

A series of time-of-flight (TOF) spectra of isolated Mn atoms were measured in the vicinity of 2p → 3d excitation states (635 to 656 eV) at a high-energy resolution. Synchrotron radiation was used as a light source. From this spectral data, charge-separated photoion-yield spectra and charge-state distribution as functions of the photon energy were obtained. The photoions resulting from the 2p → 3d excitation states are distributed from Mn+ to Mn6+, with the largest component being Mn3+ ions. Based on these spectra, the relaxation processes of the 2p → 3d excitation states are semi-quantitatively considered. For this purpose, highly excited states above the next ionization limit were calculated using the GRASP92 atomic code. It is found that single and double Auger shake-off processes play a central role in the formation of Mn5+ and Mn6+ ions. From the behavior of the charge-state distribution, the lowest 2p ionization limit has been determined to be 647.0 ± 0.3 eV. [ABSTRACT FROM AUTHOR]

With a time-of-flight (TOF) ion analyzer combined with synchrotron radiation, total photoion-yield spectrum has been measured on isolated Mn atoms in the 2p → 3d excitation region (632 eV to 657 eV) with an estimated resolution 0.065 eV. The analysis of the observed spectrum was performed with the help of ab initio calculations of the excited states using the computer code GRASP92 for the MCDF calculation and of oscillator strengths for the excitation using the related REOS program. The calculations were performed for two outer-shell configuration cases: one considering the single reference-configuration 3dm4s2 and another with the multiple reference-configuration 3dm4s2 + 3dm + 14s + 3dm + 2 (m = 5 for the ground state and m = 6 for the 2p → 3d excited states). This two-step calculation showed the CI effect in the case of the excitation of a deep inner-shell. [ABSTRACT FROM AUTHOR]

Photodouble ionization (PDI) triple-differential cross sections (TDCSs) of benzene and thiophene have been measured in electron-electron coincidence experiments under 10-10 eV and 20-20 eV equal energy sharing conditions. A multi-Gaussian fit method has been employed to characterize the TDCSs. The trends and features observed for benzene and thiophene do highlight differences with helium most likely from molecular PDI contributions to the TDCS. A comparison with the well-known helium PDI TDCS for equal energy sharing conditions [Avaldi and Huetz J. Phys. B: At. Mol. Opt. Phys. , 2005, 38 , S861-S891] supported the validity of the multi-Gaussian fitting method and contextualized the benzene and thiophene fits. The molecular targets and energy sharing conditions were chosen to provide insight into the unexpected resonances observed in aromatic hydrocarbons but not aromatic heterocyclic molecules [Wehlitz et al. , Phys. Rev. Lett. , 2012, 109 , 193001]. Contrary to the work of [Wehlitz et al. , Phys. Rev. Lett. , 2012, 109 , 193001], no significant differences between benzene and thiophene were found.

The double photoionization of Mg has been studied experimentally and theoretically in a kinematic where the two photoelectrons equally share the excess energy. The observation of a symmetrized gerade amplitude, which strongly deviates from the Gaussian ansatz, is explained by a two-electron interference predicted theoretically, but never before observed experimentally. Similar to the Cooper minima in the single photoionization cross section, the effect finds its origin in the radial extent and oscillation of the target wave function.

The radiative decay of (1)P(o) doubly excited states in helium has been investigated using a novel apparatus in which metastable atoms and vacuum ultraviolet photons are detected. The intensity ratio of the energetically narrow (sp,2n-)(1)P(o) and (2p,nd)(1)P(o) series to the broader (sp,2n+)(1)P(o) series is strikingly enhanced in comparison with conventional photoabsorption, photoion, or photoelectron measurements using synchrotron radiation. The experimental approach is a new way forward for the study of energetically narrow doubly excited states.