States Of Xe Research Articles

Octupole vibrational excitations built on shell-model states in Xe, Cs, and Ba isotopes up to mass 142

Octupole vibrational excitations built on shell-model states in Xe, Cs, and Ba isotopes up to mass 142

Ion-core switching in Rydberg series of XeKr

We investigate XeKr in high Rydberg states by mass-resolved optical-optical double resonance excitation spectroscopy. We excite XeKr via two-photon absorption to the v* = 0 and v* = 2 vibrational levels of an intermediate electronically excited state of Xe*Kr correlated to Xe*6p[5/2]2 and excite Xe*Kr further via one-photon absorption to the high Rydberg states of Xe**Kr in the energy range of 93200–97400 cm−1. The potential energy curves and the quantum defects of the d-Rydberg and s-Rydberg series of Xe**Kr, converging the A 2Π3/2 state of XeKr+ are determined. From the kinetic energy release in the predissociation process, we conclude that the ion-core switching occurs by the interaction between the bound electronic states of Xe**Kr converging to the A 2Π3/2 state of XeKr+ and the repulsive electronic states of low-lying electronic states of XeKr**. Based on numerical simulations, we interpret the dependence of the yield of the ion-core switching on the excitation energy in terms of the population transfer from the bound electronic states of the high Rydberg states Xe**Kr, converging to the A 2Π3/2 state of XeKr+, to those converging to the electronic ground X2 Σ 1 / 2 + state of XeKr + .

Evidence of Xe-incorporation in the bubble superlattice in irradiated U-Mo fuel

For years, researchers have reported competing ideas on the formation of fission gas bubble superlattices in metallic fuels, which was postulated to be comprised of elemental xenon (Xe) atoms. However, the chemical and physical arrangement of these elements within this gas bubble superlattice had not been verified. In this contribution, Xe was chemically profiled using atomic resolution scanning transmission electron microscopy (STEM) and atom probe tomography (APT) techniques in irradiated uranium-molybdenum (U-Mo) fuels. These complementary techniques provide conclusive evidence of Xe presence in the bubble superlattice up to fission densities of 4.5 × 1021 fissions/cm3 and give a quantitative assessment of Xe content within the bubble superlattice. Based on the results of simultaneous imaging and spectroscopy using STEM, the chemical composition of the Xe bubble superlattice was measured and found to be up to 8±1.3 atomic %. APT data complemented STEM findings on Xe distribution in irradiated U-Mo fuel sample. This study provides conclusive evidence that Xe is not only present within an atomically arranged bubble superlattice but provides fundamental insight into the physical state of Xe in low enriched U-Mo monolithic fuel.

Revisiting band structures in 118Xe nucleus via in-beam γ-ray spectroscopy* *The authors are grateful for the pelletron and support staff of IUAC, New Delhi. We would also like to acknowledge the contribution of the INGA collaboration, which is partially funded by the Department of Science and Technology (DST, GoI; project no. IR/S2/PF-03/2003-I) and University Grants Commission (UGC). This work was

The neutron deficient Xe nuclei with A 120 are predicted to have strong octupole correlation at low spins. In the present study, an attempt was made to improve upon the level scheme and also to examine the signatures of octupole correlation in Xe via high spin γ-ray spectroscopy. High spin states in Xe have been populated via the Nb(Si, p2n)Xe fusion-evaporation reaction at a beam energy of 115 MeV provided by the 15 UD pelletron accelerator facility at IUAC, New Delhi. In the experiment, seven new γ-transitions have been found and placed appropriately in the level scheme. A theoretical study using the triaxial projected shell model (TPSM) approach suggests that the first bandcrossing is due to the alignment of two neutrons, and a parallel band tracking the yrast configuration is the γ-band built on the two-quasiparticle state. Enhanced E1 transition rates measured between opposite parity bands involving νh and ν d orbitals having Δj = Δl = 3 indicate the presence of octupole correlation in this nucleus.

Observation of Quantum Beats of Two-Photon-Excited States of Xe upon Photoionization

Observation of Quantum Beats of Two-Photon-Excited States of Xe upon Photoionization

Investigation of kinetics of mid-infrared ASEs of Xe by two photon excitation

Optical pumped metastable rare gas lasers show great potential for high power operation. It is essential for understanding energy transfer processes between excited states of rare gas. In this work, two photon pumped laser induced amplified spontaneous emission (ASE) was used to study the kinetics of high lying state of Xe 6p'[1/2]0. Spectra and waveform of these ASEs were studied in the region of 1000–5000 nm when Xe was excited to the 6p'[1/2]0 state. Cascade transitions from the excited state were found to have two dominant channels which are 6p'[1/2]0 - 5d[1/2]1 - 6p[1/2]1 and 6p'[1/2]0–7s[3/2]1 - 6p(6p[5/2]2, 6p[3/2]1 and 6p[3/2]2). In addition, three delayed ASEs appeared when the Xe pressure is low. They are 3107 nm (5d[5/2]3 - 6p[3/2]2), 3368 nm (5d[5/2]2 - 6p[3/2]1) and 3508 nm (5d[7/2]3 - 6p[5/2]2). By the comparison of waveforms of cascade ASEs under different Xe pressures, prepared states by two photon excitation etc., it was found that 5d[5/2]3, 5d[5/2]2 and 5d[7/2]3 states of Xe were produced directly by collision relaxations and the corresponding relaxation rate constants were obtained by fitting the delay time of ASEs.

Spectator electron effects on the two-electron one-photon radiative transition process of double K hole state of Xe[formula omitted] ion([formula omitted

The double electron E1 transition energies, probabilities, and oscillator strengths between the 2s2pn and 1s22pn−1(1≤n≤6) configurations of Xeq+(47≤q≤52) ions with different spectator electrons have been calculated based on the multi-configuration Dirac-Hartree-Fock method. A reasonable electron correlation model is constructed with the aid of the active space method. The finite mass of nuclear, Breit interaction and QED effects have also been included. The calculated results are in good agreement with the available data. The theoretical spectra of different spectator electrons of the double K hole state have been predicted. The spectator electron effects on the transition spectra have been analyzed in detail. The present results will be helpful for analyzing the high energy X-ray spectrum observed from the interaction between high energy highly charged ions and the surface.

Covalent and Non-covalent Noble Gas Bonding Interactions in XeFn Derivatives (n = 2–6): A Combined Theoretical and ICSD Analysis

A noble gas bond (also known in the literature as aerogen bond) can be defined as the attractive interaction between any element of group-18 acting as a Lewis acid and any electron rich atom of group of atoms, thus following the IUPAC recommendation available for similar π,σ-hole interactions involving elements of groups 17 (halogens) and 16 (chalcogens). A significant difference between noble gas bonding (NgB) and halogen (HaB) or chalcogen (ChB) bonding is that whilst the former is scarcely found in the literature, HaB and ChB are very common and their applications in important fields like catalysis, biochemistry or crystal engineering have exponentially grown in the last decade. This article combines theory and experiment to highlight the importance of non-covalent NgBs in the solid state of several xenon fluorides [XeFn]m+ were the central oxidation state of Xe varies from +2 to +6 and the number of fluorine atoms varies from n = 2 to 6. The compounds with an odd number of fluorine atoms (n = 3 and 5) are cationic (m = 1). The Inorganic Crystal Structural Database (ICSD) strongly evidences the relevance of NgBs in the solid state structures of xenon derivatives. The ability of Xe compounds to participate in π,σ-hole interactions has been studied using different types of electron donors (Lewis bases and anions) using DFT calculations (PBE1PBE-D3/def2-TZVP) and the molecular electrostatic potential (MEP) surfaces.

Analysis of Efficiencies of Electron Capture by Ions into Rydberg States and Inelastic n → n' Transitions in Plasma of Inert Gas Mixtures

A comparative analysis of efficiencies of the resonant and nonresonant mechanisms of electron capture by ions into Rydberg states of Xe(n) atoms and inelastic n → n' transitions between highly excited levels in the inert Rg/Xe gas mixture plasma that contains atomic (Xe+) and molecular (RgXe+ and Xe$$_{2}^{ + }$$) ions (Rg = Ne, Ar, and Kr, [Xe] $$ \ll $$ [Rg]) is carried out. The rate constants of resonant electron capture by Xe+ ions in triple collisions with Rg($$^{1}{{S}_{0}}$$) atoms of an inert gas and dissociative recombination of heteronuclear (RgXe+) and homonuclear (Xe$$_{2}^{ + }$$) ions are calculated based on our approach developed within the framework of the theory of nonadiabatic transitions between electron terms of the RgXe+ + e system. For the alternative mechanism of three-particle electron capture by Xe+ ions in collisions with Ne, Ar, and Kr atoms, the rate constants are calculated in the impulse approximation with account for the short-range and polarization electron–atom interactions. The rate constants of three-particle electron capture by ions and n → n' transitions in collisions with electrons are calculated using known theoretical models. Ranges of plasma ionization degrees, plasma electron and gas temperatures, and principle quantum number of Xe atom where resonant free–bound and bound–bound electron transitions play a key role are established.

A xenon collisional-radiative model applicable to electric propulsion devices: I. Calculations of electron-impact cross sections for xenon ions by the Dirac B-spline R-matrix method

A fully relativistic Dirac B-spline R-matrix (DBSR) method is applied to calculate the oscillator strengths and electron-impact excitation cross sections involving the 5s25p5, 5s5p6, 5p46s, 5p45d, 5p46p, and 5p47s states of a Xe+ ion. A fully relativistic approach is necessary for this problem, since the spin–orbit coupling is of the same order as electron correlations in the outer shells of Xe+. Also, there is a complex open-shell structure with strong term dependence in the one-electron orbitals. The oscillator strengths are also calculated and agree well with available experimental measurements. We select some important excitation cross sections out of the ground, metastable, and quasi-metastable states of Xe+ for the collisional-radiative (CR) model to be discussed and analyzed. The present paper is the first one of a series of studies on a CR model of xenon ions in plasma diagnosis and numerical simulations of Hall and ion thrusters. In subsequent papers, the cross-section data for the Xe+ ion, together with those for neutral Xe from our previous calculation, are used to build a comprehensive CR model for electric propulsion systems involving xenon. Furthermore, the predictions of this model will then be examined by experiments in both Hall and ion thrusters.

Collisional-radiative model of xenon plasma with calculated electron-impact fine-structure excitation cross-sections

Detailed electron-impact excitation cross-section results for xenon in the wide range of incident energy from threshold to 1000 eV are calculated using relativistic distorted wave theory. Various transitions from the ground 5p6 state to the excited 5p56s, 5p56p, 5p55d, 5p57s and 5p57p as well as among these excited states are considered. The relativistic Dirac–Fock multi-configuration wave functions for the ground and excited states of Xe are obtained and used in the calculations. Where available, our cross-section results are compared with previously reported measurements and calculations. We have also fitted the calculated cross-sections through analytical formulae for plasma modeling purposes. As an application, using the obtained cross-sections, a collisional-radiative (C-R) model coupled with an optical emission measurement from the inductively coupled Xe plasma is developed and the extracted plasma parameters are reported.

The study on high <i>n</i> Rydberg state of La II

We analyze ionic spectrum of lanthanum via intermediate state (Xe)<inline-formula><tex-math id="M191">\begin{document}$ 5d6d \; ^3F_2 $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20181980_M191.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20181980_M191.png"/></alternatives></inline-formula> in the energy region 89872-91783 cm<sup>–1</sup>, and the spectrum is obtained using five-laser resonance excitation in combination with a method of sequential ionization by a pulsed electric field and a constant electric field, and has been recalibrate in this work. Both of one strong and one weak autoionization Rydberg series converging to the La<sup>2+</sup> state are determined. Meanwhile, the two autoionization Rydberg series are assigned by relativistic multichannel theory (RMCT) within the framework of multi-channel quantum defect theory (MQDT). More specifically, the strong autoionization Rydberg series is assigned to <inline-formula><tex-math id="M192">\begin{document}$ 5dnp\left(\dfrac{5}{2},\dfrac{1}{2}\right)_3 $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20181980_M192.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20181980_M192.png"/></alternatives></inline-formula> and/or <inline-formula><tex-math id="M193">\begin{document}$ 5dnp\left(\dfrac{5}{2},\dfrac{1}{2}\right)_2 $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20181980_M193.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20181980_M193.png"/></alternatives></inline-formula>, and the weak autoionization Rydberg series is assigned to <inline-formula><tex-math id="M194">\begin{document}$ 5dnf\left(\dfrac{5}{2},\dfrac{5}{2}\right)_3 $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20181980_M194.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20181980_M194.png"/></alternatives></inline-formula> and/or <inline-formula><tex-math id="M195">\begin{document}$ 5dnf\left(\dfrac{5}{2},\dfrac{5}{2}\right)_2 $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20181980_M195.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20181980_M195.png"/></alternatives></inline-formula>. We focus on the behavior of quantum defect with excitation energy for high <inline-formula><tex-math id="M196">\begin{document}$ n $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20181980_M196.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20181980_M196.png"/></alternatives></inline-formula> Rydberg states, which are sensitive to the existence of a external field. We find the breakdown of quantum defect regular behavior for a specific Rydberg series and autoionization Rydberg series of La<sup>+</sup> as the effective quantum number <inline-formula><tex-math id="M197">\begin{document}$ n^\star>67 $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20181980_M197.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20181980_M197.png"/></alternatives></inline-formula>. Due to that our calculations, which are obtained by relativistic multichannel theory and included configuration interactions, are in basically agreement with that for experimental low <inline-formula><tex-math id="M198">\begin{document}$ n $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20181980_M198.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20181980_M198.png"/></alternatives></inline-formula> (<inline-formula><tex-math id="M199">\begin{document}$ n^\star<67 $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20181980_M199.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20181980_M199.png"/></alternatives></inline-formula>) Rydberg states as well as small stray electric fields, we suggest that plasma formed by photoionization of La atoms in the second excitation step may be responsible for the breakdown of quantum defect regular behavior.

Fabrication of 122Sn target and its application in -ray spectroscopy

A self-supporting 122Sn target has been fabricated via rolling of an ingot of 99.3% enriched 122Sn at the target laboratory of Inter-University Accelerator Centre, New Delhi. The isotopic purity of the target has been verified. The prepared target has been used in a γ-ray spectroscopy experiment to study the high spin states of Xe and Te nuclei. Relative cross-sections of different evaporation channels have been extracted from experimental data and compared with the same estimated by a Monte-Carlo code, namely, Projection Angular-momentum Coupled Evaporation (PACE4). A disagreement in the experimental cross-section and PACE4 prediction has been reported for the α3n channel.

Electron-impact excitation of Xe+ and polarization of its subsequent emissions

Fully relativistic distorted wave calculations have been performed to study the electron impact excitation of singly ionized xenon from its ground 5p5 (J = 3/2) state to different fine structure excited states of the 5p46s, 5p46p, 5p47s, 5p47p, 5p45d and 5p46d configurations. The ground and excited bound states of Xe+ion have been represented through the relativistic multi-configuration Dirac-Fock wave functions while projectile electron distorted continuum wave functions are obtained by solving the Dirac equations. Results are reported for the excitation cross sections and the corresponding rate-coefficients of the considered different transitions. For each transition, analytic fitting to the calculated cross sections are also provided for plasma modeling purposes. In addition, using the density matrix theory and the calculated different magnetic sub-level excitation cross sections the linear polarization of the radiation emitted by the different optically allowed transitions are obtained and presented.

Selectivity of Electronic Coherence and Attosecond Ionization Delays in Strong-Field Double Ionization.

Experiments are presented on real-time probing of coherent electron dynamics in xenon initiated by strong-field double ionization. Attosecond transient absorption measurements allow for characterization of electronic coherences as well as relative ionization timings in multiple electronic states of Xe^{+} and Xe^{2+}. A high degree of coherence g=0.4 is observed between ^{3}P_{2}^{0}-^{3}P_{0}^{0} of Xe^{2+}, whereas for other possible pairs of states the coherences are below the detection limits of the experiments. A comparison of the experimental results with numerical simulations based on an uncorrelated electron-emission model shows that the coherences produced by strong-field double ionization are more selective than predicted. Surprisingly short ionization time delays, 0.85fs, 0.64fs, and 0.75fs relative to Xe^{+} formation, are also measured for the ^{3}P_{2}, ^{3}P_{0}, and ^{3}P_{1} states of Xe^{2+}, respectively. Both the unpredicted selectivity in the formation of coherence and the subfemtosecond time delays of specific states provide new insight into correlated electron dynamics in strong-field double ionization.

Low-temperature photoionized plasmas induced in Xe gas using an EUV source driven by nanosecond laser pulses

AbstractIn this work, a laser-produced plasma source was used to create xenon (Xe) photoionized plasmas. An extreme ultraviolet (EUV) radiation beam was focused onto a gas stream, injected into a vacuum chamber synchronously with the EUV pulse. Energies of photons exceeding 100 eV allowed for inner-shell ionization of Xe atoms. Creation ofN-shell vacancies resulted inN-shell fluorescence and was followed by multiple ionization. Time-integrated EUV spectra, corresponding to excited states in Xe II–V ions, were recorded. Several emission lines detected in the 39–65 nm wavelength range were not reported earlier. They were not identified due to lack of a corresponding information in published databases. Except spectral measurements in the EUV range, time resolved ultraviolet and visible spectra, originating from Xe II and III ions, were recorded. For spectral lines, corresponding to radiative transitions in Xe II ions, electron temperature was calculated based on a Boltzmann plot method. Based on this method the temperature was measured for different time delays according to the driving EUV pulses.

Kerr self-defocusing of multiple filaments in TW peak power UV laser beam

An effective suppression of multiple filamentation of the sub-TW peak power supercritical laser beam in xenon gas was demonstrated in direct amplification of subpicosecond UV pulses at Ti:sapphire/KrF laser facility GARPUN-MTW. A large negative nonlinear refractive index due to a two-photon resonance of KrF laser radiation with Xe state ensured Kerr self-defocusing of a few hundred filaments with a local peak intensity of ~0.2 TW cm−2, 200-fold higher than the average one over the beam cross section, and thus homogenized the laser beam. UV filaments in Xe produced a narrow-angle monochromatic coherent cone emission at 828 nm wavelength due to stimulated hyper-Raman scattering and amplified spontaneous emission at the transition .

Electron transfer mediated decay in NeXe triggered by K-LL Auger decay of Ne

In this article we present the results of an ab initio study of electron transfer mediated decay (ETMD) in NeXe dimer triggered by the K-LL Auger decay of Ne. We found that the Ne2+(2p-21D)Xe and Ne2+(2p-21S)Xe states which are strongly populated in the Auger process may decay by ETMD emitting a slow electron and leading to the Coulomb explosion of the dimer which results in Ne+ and Xe2+ ions. We also computed the corresponding decay widths, the ETMD electron spectra, and the kinetic energy release of the nuclei (KER) spectra. We showed that the spectra corresponding to the decaying states which derive from the two multiplets have completely different shape which reflects differing accessibility of the ETMD final states. Thus, in the Ne2+(2p-21S)Xe state ETMD is allowed for all interatomic distances accessible in nuclear dynamics, while in the Ne2+(2p-21D)Xe state the ETMD channels become closed one by one. This in turn leads to the different behavior of the ETMD decay widths and ultimately the spectra. We show how these differences make it possible to study ETMD of the two states separately in a coincident measurement. We also discuss how the dynamics which follow ETMD in the final state manifold may lead to the appearance of the unusual products: Ne, Xe3+ and a slow electron.

Relativistic photoionization delays and the role of auto-ionizing resonances

SynopsisWe measured the relative ionization delays into the two spin-orbit components of the electronic ground states of Xe+ and Kr+ under the inuence of auto-ionizing intermediate and final states. The results are in good agreement with state-of-the-art calculations based on the time-dependent configuration-interaction singles (TDCIS) approach.

Recombination dynamics of clusters in intense extreme-ultraviolet and near-infrared fields

We investigate electron-ion recombination processes in clusters exposed to intense extreme-ultraviolet (XUV) or near-infrared (NIR) pulses. Using the technique of reionization of excited atoms from recombination (REAR), recently introduced in Schütte et al (2014 Phys. Rev. Lett. 112 253401), a large population of excited atoms, which are formed in the nanoplasma during cluster expansion, is identified under both ionization conditions. For intense XUV ionization of clusters, we find that the significance of recombination increases for increasing cluster sizes. In addition, larger fragments are strongly affected by recombination as well, as shown for the case of dimers. We demonstrate that for mixed Ar–Xe clusters exposed to intense NIR pulses, excited atoms and ions are preferentially formed in the Xe core. As a result of electron-ion recombination, higher charge states of Xe are efficiently suppressed, leading to an overall reduced expansion speed of the cluster core in comparison to the shell.