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Register a new userTheoretical investigation of spectroscopic properties of W$^{26+}$ in EBIT plasma
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Energy levels, radiative transition wavelengths and probabilities have been studied for the W$^{26+}$ ion using multiconfiguration Dirac-Fock and Dirac-Fock-Slater methods. Corona and collisional-radiative models have been applied to determine lines and corresponding configurations in a low-density electron beam ion trap (EBIT) plasma. Correlation effects for the $4f^{2}$, $4d^{9}4f^{3}$, $4f5l$ ($l=0,...,4$), $4fng$ ($n=5, 6, 7$) configurations have been estimated by presenting configuration interaction strengths. It was determined that correlation effects are important for the $4f5s rightarrow 4f^{2}$ transitions corresponding to weak electric octupole transitions in a single-configuration approach. Correlation effects influence the $4f5d rightarrow 4f^{2}$ transitions by increasing transition probabilities by an order of magnitude. Identification of some lines observed in fusion plasma has been proposed. Spectra modeling shows strong increase of lines originating from the $4f5s rightarrow 4f^{2}$ transitions. Other transitions from the $10-30$ nm region can be of interest for the EBIT plasma.
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Energy levels and emission spectra of $W^{25+}$ ion have been studied by performing the large-scale relativistic configuration interaction calculations. Configuration interaction strength is used to determine the configurations exhibiting the largest influence on the $4f^{3}$, $4d^{9}4f^{4}$, $4f^{2}5s$, $4f^{2}5p$, $4f^{2}5d$, $4f^{2}5f$, $4f^{2}5g$, and $4f^{2}6g$ configuration energies. It is shown that correlation effects are crucial for the $4f^{2}5s rightarrow 4f^{3}$ transition which in single-configuration approach occurs due to the weak electric octupole transitions. As well, the correlation effects affect the $4f^{2}5d rightarrow 4f^{3}$ transitions by increasing transition probabilities by an order. Corona model has been used to estimate the contribution of various transitions to the emission in a low-density electron beam ion trap (EBIT) plasma. Modeling in 10--30 nm wavelength range produces lines which do not form emission bands and can be observed in EBIT plasma.
A detailed level collisional-radiative model of the E1 transition spectrum of Ca-like W$^{54+}$ ion has been constructed. All the necessary atomic data has been calculated by relativistic configuration interaction (RCI) method with the implementation of Flexible Atomic Code (FAC). The results are in reasonable agreement with the available experimental and previous theoretical data. The synthetic spectrum has explained the EBIT spectrum in 29.5-32.5 AA ,, while several new strong transitions has been proposed to be observed in 18.5-19.6 AA , for the future EBIT experiment with electron density $n_e$ = $10^{12}$ cm$^{-3}$ and electron beam energy $E_e$ = 18.2 keV.
Plasma diagnostics in magnetic confinement fusion plasmas by using visible spectrum strongly depends on the knowledge of fundamental atomic properties. A detailed collisional-radiative model of W$^{26+}$ ions has been constructed by considering radiative and electron excitation processes, in which the necessary atomic data had been calculated by relativistic configuration interaction method with the implementation of Flexible Atomic Code. The visible spectrum observed at an electron beam ion trap (EBIT) in Shanghai in the range of 332 nm to 392 nm was reproduced by present calculations. Some transition pairs of which the intensity ratio are sensitive to the electron density were selected as potential candidate of plasma diagnostics. Their electron density dependence are theoretically evaluated for the cases of EBIT plasmas and magnetic confinement fusion plasmas.
The experimental characterization of scattering resonances in low energy collisions has proven to be a stringent test for quantum chemistry calculations. Previous measurements on the NO-H$_2$ system at energies down to $10$ cm$^{-1}$ challenged the most sophisticated calculations of potential energy surfaces available. In this report, we continue these investigations by measuring the scattering behavior of the NO-H$_2$ system in the previously unexplored $0.4 - 10$ cm$^{-1}$ region for the parity changing de-excitation channel of NO. We study state-specific inelastic collisions with both textit{para}- and textit{ortho}-H$_2$ in a crossed molecular beam experiment involving Stark deceleration and velocity map imaging. We are able to resolve resonance features in the measured integral and differential cross sections. Results are compared to predictions from two previously available potential energy surfaces and we are able to clearly discriminate between the two potentials. We furthermore identify the partial wave contributions to these resonances, and investigate the nature of the differences between collisions with textit{para}- and textit{ortho}-H$_2$. Additionally, we tune the energy spreads in the experiment to our advantage to probe scattering behavior at energies beyond our mean experimental limit.
In order to realize more sensitive eEDM measurement, it would be worthwhile to find some new laser-cooled molecules with larger internal effective electric field (E$_{eff}$), higher electric polarizability and longer lifetime of the eEDM measurement state. Here we explore the merits of mercuric monofluoride ($^{202}Hg^{19}F$, X$^ 2 {Sigma}_{1/2}$) for its potential of laser cooling and eEDM measurement. We theoretically investigated the electronic, rovibrational and hyperfine structures and verified the highly diagonal Franck-Condon factors (FCFs) of the main transitions by the Rydberg-Klein-Rees inversion (RKR) method and the Morse approximation. Hyperfine manifolds of the X$^ 2 {Sigma}_{1/2} ( u=0$) rotational states were examined with the effective Hamiltonian approach and a feasible sideband modulation scheme was proposed. In order to enhance optical cycling, the microwave remixing method was employed to address all the necessary levels. The Zeeman effect and the hyperfine structure magnetic g factors of the X$^ 2 {Sigma}_{1/2} ( u=0$,$mathit{ N } $=1) state were studied subsequently. Finally, its statistical sensitivities for the eEDM measurement were estimated respectively to be about $9times 10^{-31} ebullet cm $ (the laser cooled transverse beam experiment), $2times 10^{-31} ebullet cm$ (the fountain experiment) and $1times 10^{-32}$ ebullet cm (experiment with trapped cold molecules), indicating that $^{202}Hg^{19}F$ might be another promising eEDM candidate when compared with the most recent ThO result of $d_{ e } = (4.3 pm 3.1_{ stat } pm 2.6_{ syst })times 10^{-30} ebullet cm$ (Nature, 562, 355 (2018)). In addition, the possibility of direct Stark decelerating of the HgF radical was also discussed.
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