We report the observation of trielectronic recombination with simultaneous excitation of a K-shell and an L-shell electron, hence involving three active electrons. This process was identified in the x-ray emission spectrum of recombining highly charged Kr ions. An energy resolution three times higher than any reported for this collision energy range around 10 keV resulted in the separation of the associated lines from the stronger dielectronic resonances. For Kr 30+ , intershell trielectronic recombination contributions of nearly 6% to the total resonant photorecombination rate were found.Electron-electron interaction mediates the strongest atomic processes such as dielectronic recombination ͑DR͒ and its time reversal, Auger decay, following photoexcitation of an inner-shell electron ͓1,2͔. Higher-order electron correlation plays also an essential role; however, these relevant processes are difficult to approach, both experimentally and theoretically. In the simple DR process involving only two interacting electrons, as sketched in Fig. 1 ͑left side͒, the kinetic energy of the recombined electron is transferred to a single bound electron by a radiationless excitation to an intermediate autoionizing state. The recombination is completed by its radiative stabilization. For the case of highly charged ions ͑HCIs͒, radiative transition probabilities are high, and the competition of radiative deexcitation and Auger decay of the intermediate state is biased toward the first mechanism.Beyond the well-known DR, resonant recombination processes involving higher-order correlations are relevant, too. Here, as displayed in Fig. 1, two or even three bound electrons can be simultaneously excited by the resonantly captured electron in trielectronic or even quadruelectronic recombination ͑TR and QR, respectively͒.Here, we present evidence for "intershell" TR involving excitation of a K-shell electron simultaneously with one of the L shells and provide a comparison with our theoretical predictions. TR and QR resonance energies and cross sections were predicted in the framework of the multiconfiguration Dirac-Fock ͑MCDF͒ method. Weak experimental signatures of intershell QR are also found at their calculated values. The processes we investigated are denoted as KL-LLL TR and KLL-LLLL QR, where the first set of capital letters indicates the initial shells of the bound electrons and the second one refers to the shells of the captured and excited electrons. In contrast to the already reported "intrashell" TR ͓3͔, for intershell higher-order processes the electron overlap is correspondingly smaller. Moreover, for higher atomic numbers the e-e correlation gets relatively weaker compared to the central force.Resonant mechanisms are highly efficient in either ionizing or recombining ions and hence already DR is of paramount importance for the physics of outer planetary atmospheres and interstellar clouds as well as an important radiative cooling mechanism in astrophysical and laboratory high-temperature plasmas ͓1,2,4͔. DR often represents...
The dynamics of COVID-19 is investigated with regard to complex contributions of the omitted factors. For this purpose, we use a fractional order SEIR model which allows us to calculate the number of infections considering the chaotic contributions into susceptible, exposed, infectious and removed number of individuals. We check our model on Wuhan, China-2019 and South Korea underlying the importance of the chaotic contribution, and then we extend it to Italy and the USA. Results are of great guiding significance to promote evidence-based decisions and policy.
Resonance fluorescence of laser-driven highly charged ions is studied in the relativistic regime by solving the time-dependent master equation in a multi-level model. Our ab initio approach based on the Dirac equation allows for investigating highly relativistic ions, and, consequently, provides a sensitive means to test correlated relativistic dynamics, bound-state quantum electrodynamic phenomena and nuclear effects by applying coherent light with x-ray frequencies. Atomic dipole or multipole moments may be determined to unprecedented accuracy by measuring the interferencenarrowed fluorescence spectrum.PACS numbers: 78.70. En,31.30.Jv,32.70.Jz,31.30.Gs High-precision laser spectroscopy has resulted in crucial advancements in our understanding of nature. In particular, optical laser spectroscopy (OS) is a versatile tool to investigate correlated relativistic quantum dynamics, the testing of fundamental theories like quantum electrodynamics (QED) [1,2] or parity non-conservation in atomic systems. The determination of atomic dipole or multipole moments via lifetime measurements by means of, e.g., visible emission spectroscopy [3], approaching the accuracy of one per thousand, sheds light on QED effects like the electron anomalous magnetic moment. Isotope shifts (IS) in atomic spectra which has been providing valuable insight into the collective structure of nuclei: for example, recently, isotope shifts were determined by collinear laser spectroscopy [4]. Beyond purely nuclear effects, the interaction of the correlated motion of electrons and that of the nucleus can be studied in IS measurements: recently, relativistic effects on nuclear recoil have been measured in visible forbidden transitions of few-electron argon ions by a trapped-ion method [5].In the regime of heavy few-electron systems, however, the accuracy of optical spectroscopy can seldom be exploited due to the scarcity of low-frequency transitions. Therefore, one has to apply other techniques. Measuring x-ray emission lines of highly charged uranium ions confined in an electron beam ion trap allowed testing highfield QED on the two-loop level [1] and delivered a new value for the radius of the radioactive isotope 235 U [6]. Recently, a method based on the storage ring measurement of dielectronic recombination spectra yielded the change of charge radii for neodymium isotopes [7,8].With the advent of modern short-wavelength laser systems, the accuracy and versatility of laser spectroscopy may be combined with the increased sensitivity of highly charged ions (HCI) to relativistic and QED effects, nuclear properties, and this may also give new information on HCI structure and dynamics relevant in astrophysical and thermonuclear plasmas. Brilliant x-ray light has already enabled to study transitions in the soft x-ray regime involving HCI [9]. Coherent light with photon energies over 10 keV becomes accessible in the near future [10], allowing for an extension to heavier systems and the exploitation of coherence properties. This would also ask for the va...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.