类Be离子（Z=8-54）内壳层激发态1s2s22p退激发过程的理论研究

采用基于全相对论框架的多组态Dirac-Fock方法,系统研究了类Be离子（Z=8-54）内壳层激发态1s2s22p的能量、辐射退激发和Auger退激发过程。详细讨论了电子关联效应对相关结构和退激发过程的影响。结果表明,来自于n=2和3壳层的电子关联效应最重要。另外,随着Z的增大,辐射退激发几率逐渐而平滑的增大,而Auger退激发几率的变化则不显著。本文计算结果与其它理论计算结果符合很好。     

类Be离子(Z=8-54)内壳层激发态1s2s~22p退激发过程的理论研究

采用基于全相对论框架的多组态Dirac-Fock方法,系统研究了类Be离子(Z=8-54)内壳层激发态1s2s22p的能量、辐射退激发和Auger退激发过程.详细讨论了电子关联效应对相关结构和退激发过程的影响.结果表明,来自于n=2和3壳层的电子关联效应最重要.另外,随着Z的增大,辐射退激发几率逐渐而平滑的增大,而Auger退激发几率的变化则不显著.本文计算结果与其它理论计算结果符合很好.     

类Li硼离子内壳层三重激发态2s2p~2的结构和俄歇过程

采用基于全相对论框架的多组态Dirac-Fock方法,研究了类Li硼离子内壳层三重激发态2s2p~2的结构和俄歇退激发过程.为了充分考虑电子关联效应,将活动空间扩展到n=8壳层.详细讨论了电子关联效应对类Li硼离子内壳层三重激发态2s2p~2结构和俄歇退激发过程的影响.结果表明,在对类Li硼离子内壳层三重激发态2s2p~2进行理论研究时,有必要考虑来自n=8壳层的电子关联效应.本文模拟的类Li硼离子内壳层三重激发态2s2p~2的俄歇电子谱与实验符合好.     

类Li硼离子内壳层三重激发态2s2p2的结构和俄歇过程

采用基于全相对论框架的多组态Dirac-Fock方法,研究了类Li硼离子内壳层三重激发态2s2p2的结构和俄歇退激发过程。为了充分考虑电子关联效应,将活动空间扩展到n=8壳层。详细讨论了电子关联效应对类Li硼离子内壳层三重激发态2s2p2结构和俄歇退激发过程的影响。结果表明,在对类Li硼离子内壳层三重激发态2s2p2进行理论研究时,有必要考虑来自n=8壳层的电子关联效应。本文模拟的类Li硼离子内壳层三重激发态2s2p2的俄歇电子谱与实验符合好。     

Studies on odd-parity states of the Sm atom

Two-step excitation and ionization processes are used to detect Sm atoms in many excited states populated with tunable lasers. The wavelength of the first laser is tuned to the resonances from the Sm 4f^6 6s^2 ^7FJ （J=0 6） states to many odd-parity states with different electronic configurations, where the atoms are detected by photoionization process using an ultraviolet laser with a wavelength of 355 nm. Precise measurements on the energy level and intensity for many Sm 4f^6 6s6p and 4f^5 5d6s^2 states have been carried out. In a theoretical analysis on the spectral data, such as peak position, relative intensity, many transitions can be identified as the resonances from the Sm 4f^6 6s^2 7FJ （J=0-6） states to the atomic states with 4f^6 6s6p and 4f^5 5d6s^2 electronic configurations. This work also reports many spectral data on the odd-parity states that cannot be found in the literature.     

Transition probabilities for NII 2p4f-2p3d and 2s2p^23d-2s2p^23p obtained by a semiclassical method

Based on NII spectra, some transition probabilities for 2p4f--2p3d and 2s2p$^2$3d--2s2p$^2$3p are obtained by a semiclassical method. The results are in good agreement with other measurements and the data reported by the National Institute of Standards and Technology. The transition probability for a line of 424.18nm is reported for the first time. Meanwhile, a feasible method of calculating transition parameters related to special excited configurations or highly excited states is provided.     

Nuclear dissociation after the O 1s $\rightarrow (^4\Sigma_\text{u}^-)$3sσ excitation in O$_2$ molecules

We investigate the dissociation dynamics of core-excited $\mathrm{O}_2$ molecules using a high-resolution energy-resolved electron-ion coincidence experimental setup. The excited cationic states with two valence holes and one Rydberg electron are created after spectator Auger decay induced by $\mathrm{O}$ 1s $\rightarrow (^4\Sigma_{\rm u}^-)3{\rm s}\sigma$ core excitation in $\mathrm{O}_2$. From the energy correlation between the kinetic energy of the Auger electron and the ion kinetic energy release, we distinguish several dissociation channels. Rather complex dissociation channels of the spectator Auger final states are disclosed, which can be explained by the increased number of the crossing point due to the existence of Rydberg electron. The quantum system will evolve into different dissociation limits at each crossing point between the potential energy curves.     

Transition energy and dipole oscillator strength for 1s22p-1s2nd of Cr2l+ ion

The transition energies, wavelengths and dipole oscillator strengths of 1s^22p-1s^2nd （3 ≤ n ≤ 9） for Cr^21＋ ion are calculated. The fine structure splittings of 1s^2nd （n ≤ 9） states for this ion are also calculated. In calculating energy, we have estimated the higher-order relativistic contribution under a hydrogenic approximation. The quantum defect of Rydberg series 1s^2nd is determined according to the quantum defect theory. The results obtained in this paper excellently agree with the experimental data available in the literature. Combining the quantum defect theory with the discrete oscillator strengths, the discrete oscillator strengths for the transitions from initial state 1s^22p to highly excited 1s^2nd states （n ≥ 10） and the oscillator strength density corresponding to the bound-free transitions are obtained.     

Multiple Auger Decay Following Xe~+(4p_(3/2)~(-1)) Ionization

The Auger decay for the many-electron Xe~+(4p_(3/2)~(-1)) state is studied in detail,using multistep approaches.It is found that the single Auger decay channels are primarily Coster-Kronig processes,which is in accord with other theoretical and experimental results.The double and triple Auger decays result primarily from cascade processes,i.e.,the sequential two-step and three-step Auger decay,and as such,the contributions from direct processes can be neglected.Level-to-level rates for single,double,and triple decays are obtained,based on which comprehensive Auger electron spectra and ion yields are obtained.Our decay paths and Auger electron spectra are in agreement with the experimental analysis [Hikosaka et al.,Phys.Rev.A 76(2007) 032708],and our ion yield ratios(Xe~(2+):Xe~(3+):Xe~(4+)=4.6:87.0:8.4) are also in line with their values(5.0:86.0:9.0).However,with respect to the ion yield ratios,a discrepancy still remains among the experimental and theoretical results.Taking into account the complexity of Xe's electronic structure,further,more detailed experiments are still required.     

Experimental evidence of interatomic coulombic decay from the auger final states in argon dimers

Interatomic Coulombic decay (ICD) from an Auger-final dicationic state is observed in the Ar dimer. A 2p inner-shell vacancy created by photoionization is replaced with 3s and 3p vacancies via intra-atomic Auger decay. The Auger-final dicationic state is subject to ICD in which one of the 3p electrons in the same Ar atom fills the 3s vacancy while one of the 3p electrons from the neighboring Ar atom is emitted as an ICD electron. This ICD process is unambiguously identified by electron-ion-ion coincidence spectroscopy in which the kinetic energy of the ICD electron and the kinetic energy release between Ar+ and Ar2+ are measured in coincidence.     

Energies, Auger and radiative probabilities of the doubly-excited 1s23l3l′ states for Be-like neon

Energy levels, Auger decay and radiative transition rates of the doubly-excited 1s ²3l3l′ states for Be-like neon are calculated using relativistic Multiconfiguration Dirac-Fock (MCDF) method. Electron correlation and relaxation effects are taken into account. The magnitude of Auger rates for the 35 doubly-excited states and their decay channels are discussed. Present calculated values are in agreement with the latest experimental electron spectra as well as other theoretical results.     

Decay channel dependence of the photoelectron angular distributions in core-level ionization of Ne dimers

For K-shell photoionization of neon dimers, we report Ne 1s photoelectron angular distributions for Ne2++Ne+ and Ne++Ne+ channels exhibiting quite different patterns. Noninversion-symmetric patterns of the former obtained by the fast interatomic Coulombic decay of Auger final states show direct evidence of core-hole localization. Dipolar patterns of the latter obtained by the slow radiative decay of the other Auger final states clearly show that the radiative process is slow enough to allow dicationic dimers to rotate many times before fragmentation.     

Unveiling and driving hidden resonances with high-fluence, high-intensity x-ray pulses

We show that high fluence, high-intensity x-ray pulses from the world's first hard x-ray free-electron laser produce nonlinear phenomena that differ dramatically from the linear x-ray-matter interaction processes that are encountered at synchrotron x-ray sources. We use intense x-ray pulses of sub-10-fs duration to first reveal and subsequently drive the 1s?2p resonance in singly ionized neon. This photon-driven cycling of an inner-shell electron modifies the Auger decay process, as evidenced by line shape modification. Our work demonstrates the propensity of high-fluence, femtosecond x-ray pulses to alter the target within a single pulse, i.e., to unveil hidden resonances, by cracking open inner shells energetically inaccessible via single-photon absorption, and to consequently trigger damaging electron cascades at unexpectedly low photon energies.     

Cs Ⅳ离子4d内壳层激发态衰变过程的相对论理论研究

在相对论多组态Dirac-Fock理论方法基础上,通过系统考 虑电子关联效应和由于内壳层电子激发而导致的电子自旋-轨道波函数的弛豫效应,详细研究了Cs Ⅳ离子的4d内壳层电子激发组态4d95s25p5、辐射末态4d105s25p4及Auger末态4d105s25p3和4d105s15p4的能级结构及各种可能的辐射和Auger衰变过程.获得了与已有的实验结果和相关的半经 验准相对论组态相互作用计算结果相符的辐射跃迁能、振子强度以及线宽,预言了4d95s25p5态的以Auger衰变为主的 Auger电子谱的特 关键词： 内壳层激发态 辐射衰变 Auger衰变     

Observation and characterization of the fluorescence decay of the 2s2p(6)np 1P(o) excited states of Ne

Fluorescence decay of the 2s2p(6)np (1)P(o) excited states of neon has been observed directly for the first time. This process has also been observed indirectly by threshold photoelectron spectroscopy and in electron/photon coincidences. The measurements have allowed this weak decay channel to be characterized and branching ratios derived. The fluorescence excitation spectrum is well described by a simple Rydberg model that highlights the interplay and competition between the decay channels of autoionization and fluorescence.     

Theoretical study on decay of the 4d core-excited states of Cs III

In a recent XUV photoabsorption spectrum of Cs Ⅲ ions by Cummings and O＇Sullivan [2001 J. Phys. B 34 199], rather large linewidths were found for the 4d^95s^25p^6 - 4d^105s^25p^5 transition which are quite in disagreement with corresponding quasi-relativistic multiconfiguration Hartree Fock （MCHF） calculation. In the present work, a detailed multiconfiguration Dirac-Fock study has been carried out to explore this discrepancy. Owing to the detailed consideration of electron correlation effects, some ‘forbidden＇ Auger decay channels, such as 4d^105s^25p^35d and 4d^105s^05p^6, would become ‘open＇. As a result, remarkable improvement of the linewidths has been obtained in our calculation. Furthermore, the theoretical Auger spectrum of the 4d^ 95s^25p^6 core-excited states of Cs Ⅲ ions is Riven in the present work.     

Double core hole creation and subsequent Auger decay in NH3 and CH4 molecules

Energies of the hollow molecules CH(4)(2+) and NH(3)(2+) with double vacancies in the 1s shells have been measured using an efficient coincidence technique combined with synchrotron radiation. The energies of these states have been determined accurately by high level electronic structure calculations and can be well understood on the basis of a simple theoretical model. Their major decay pathway, successive Auger emissions, leads first to a new form of triply charged ion with a core hole and two valence vacancies; experimental evidence for such a state is presented with its theoretical interpretation. Preedge 2-hole-1-particle (2h-1p) states at energies below the double core-hole states are located in the same experiments and their decay pathways are also identified.     

Insulating properties of ultrathin KF layers on Cu(1 0 0): Resonant Auger spectroscopy

Solid-state effects in the creation and decay of K 2p core excitations in thin KF films on Cu(1 0 0) surface have been studied in resonant Auger spectra, excited using synchrotron radiation. The spectra of films of various thickness starting from a single monolayer were measured.The photoabsorption spectra reveal crystal field splitting already at film thickness of about 1 monolayer. The Auger decay spectra of the K 2p⁻¹3d core excitations in films of thickness up to 2 monolayers exhibit a band characteristic of the decay of core ionised states, showing that the excited electron delocalises into substrate before the core hole decays. In thicker films the coexistence of the decay of excited states in the bulk of the KF crystalline film and of ionised states at the KF-metal interface is observed, indicating that the charge transfer probability from the upper layers of the film into the metallic substrate is strongly reduced.     

Many-electron effects in the Auger-photoelectron coincidence spectroscopy spectra of the late 3d-transition metals

The valence hole created by the L2–L3 M45 Coster–Kronig (CK) transition may hop away from the ionized atomic site before the L3-hole decays. Then when the third (Auger) electron emitted by the L3-hole decay is measured in coincidence with the photoelectron emitted by the initial L2-level electron ionization, the coincidence spectrum becomes similar or identical to the singles spectrum of the secondary (Auger) electron emitted by the L3-hole decay as if it decayed as an initial single core hole. Thus the coincidence spectrum is essentially governed by the valence-hole dynamics of both the intermediate states and the final states of the L2–L3 (M45) CK-transition preceded Auger transition. In the present paper the Auger-photoelectron coincidence spectroscopy (APECS) spectra of Fe, Co, and Ni metals reported by C.P. Lund et al. (Phys. Rev. B55 (1997) 5455) are analyzed in light of the delocalization and localization of the valence hole(s) created by the CK transition or the CK-transition preceded Auger transition.     

Circular polarization of ion fluorescence completing the analysis of resonant Xe* 4d(-1)(5/2)6p Auger decay

The relative contributions of the partial electron waves emitted in the Auger decay of the Xe* 4d(-1)(5/2)6p(J(*)=1) resonance have been determined by fluorescence polarimetry after excitation with circularly polarized synchrotron radiation. The analysis of circularly polarized fluorescence of the photoion leads to an independent determination of the orientation parameters for all states of the Xe II 5p(4)6p multiplet. The present study provides, in combination with data on the angular distribution and spin polarization of the Auger electrons, complete quantum mechanical information on the resonant Auger decay, i.e., branching ratios and relative phases of the Auger decay amplitudes.