Multiple excitation in photoionization using B-splines

By carefully following the spatial and temporal criteria of the Debye-Hückel (DH) approximation, we present a detailed theoretical study on the redshifts of the spectroscopically isolated He α lines corresponding to the 1s2p 1 P → 1s 2 1 S emission from two-electron ions embedded in external dense plasma. We first focus our study on the ratio R = ω α /ω o between the redshift ω α due to the external plasma environment and the energy ω o of the He α line in the absence of the plasma. Interestingly, the result of our calculation shows that this ratio R turns out to vary as a nearly universal function of a reduced Debye length λ D (Z) = (Z − 1)D. Since the ratio R dictates the necessary energy resolution for a quantitative measurement of the redshifts and, at the same time, the Debye length D is linked directly to the plasma density and temperature, the dependence of R on D should help to facilitate the potential experimental efforts for a quantitative measurement of the redshifts for the He α line of the two-electron ions. In addition, our study has led to a nearly constant redshift ω α at a given D for all He-like ions with Z between 5 and 18 based on our recent critical assessment of the applicability of the DH approximation to atomic transitions. These two general features, if confirmed by observation, would offer a viable and easy alternative in the diagnostic efforts of the dense plasma.

Section: Theoretical Procedures Based On the Debye-hückel Approximmentioning

confidence: 99%

Redshift of the Heα emission line of He-like ions under a plasma environment

Fang

Gao

et al. 2017

“…Recent applications of B-spline-based methods to continuum, e.g., B-spline-based configuration-interaction (BSCI) method for single continuum [1] and B-spline-based Kmatrix (BSK) method for multiple continua [2,3], have shown the effectiveness of such methods to the study of doubly excited resonances for two-electron and divalent atoms [2,4]. A straightforward application of these two methods requires rapidly increasing computational effort as the number of ionization channel increases.…”

Section: Introductionmentioning

confidence: 99%

B-spline-based complex-rotation method with spin-dependent interaction

Fang

Chang

2007

We present a B-spline-based complex-rotation ͑BSCR͒ method with spin-dependent interaction for the study of atomic photoionization leading to multiple ionization channels dominated by doubly excited resonances for two-electron and divalent atoms. The degree of mixing between different spin states and between the bound and continuum components of the state function of the resonance state can be easily identified in the BSCR method. Its application to Mg photoionization gives good agreement with observed singlet-triplet mixed Mg spectra.

“…a) shows the static optical density OD = −log 10 (I t /I 0 ) of xenon in the absence of the NIR pulse, where I 0 is the measured XUV intensity without xenon and I t is the XUV intensity transmitted through the gas sample. The 5s5p6 np autoionizing states with n={6,7,8,9} are clearly visible as window resonances[24] superimposed on a continuous absorption background.Figure 2(b) depicts the optical density for different time delays between the XUV and the NIR pulse, averaged over 20 time scans with 2 s of integration time for each delay step. A step size of 3 fs was chosen for convenience; smaller values down to 60 as are nevertheless possible.…”

mentioning

confidence: 99%

High-spectral-resolution attosecond absorption spectroscopy of autoionization in xenon

Bernhardt

Beck

et al. 2014

The decay of highly excited states of xenon after absorption of extreme ultraviolet light is directly tracked via attosecond transient absorption spectroscopy using a time-delayed near-infrared perturbing pulse. The lifetimes of the autoionizing 5s5p 6 6p and 5s5p 6 7p channels are determined to be (21.9 ± 1.3) fs and (48.4 ± 5.0) fs, respectively. The observed values support lifetime estimates obtained by traditional linewidth measurements. The experiment additionally obtains the temporal evolution of the decay as a function of energy detuning from the resonance center, and a quantum mechanical formalism is introduced that correctly accounts for the observed energy dependence.