Electron-impact single ionizaiton for W ⁴⁺ and W ⁵⁺

Abstract

Electron-impact single ionization cross sections for W q+ (q = 4-5) were calculated using the flexible atomic code (FAC) in the level-to-level distorted-wave method, considering the explicit branching ratio. The calculated cross sections are compared with the available theoretical and experiment results in detail. In the case of the contribution from the same channles as the available theoretical results, all of the calculated ionization cross sections agree with the experimental measured cross sections. But the present calculated results are larger than the experimental measurement when all channels contributions are included. Some important channels excitation autoionization (EA) contributions, such as the excitation to higher higher nl subshell from 4f and 5[s,p], were not included into the available theoretical calculation. In general, the distorted-wave (DW) results are overestimated.

Synchrotron Radiation from Electrons with a Pitch-angle Distribution

“…The broad-pulse is asymmetric with the later part of the decaying segment defined by the curvature effect Uhm & Zhang 2016). The curvature effect tail extends to the Xray band, defining a steep-decay phase with rapid spectral evolution consistent with the observations (Zhang et al 2007). The pitch-angle effect presented above does not modify such a general picture significantly.…”

The Shallow Decay Segment of GRB X-Ray Afterglow Revisited

“…After 6 months data accumulating, a five-segment canonical X-ray afterglow light curve was proposed (Zhang et al 2006), including a distinct rapidly decaying component, a shallow decay component, a normal decay component, a post jet break component and X-ray flares. With 2 years data collecting (with ∼ 100 GRBs), a series of systematic analysis of the Swift XRT data was performed, in order to explore the physical origin for each segment of the canonical light curve (Zhang et al 2007b;Liang et al 2007;Willingale et al 2007;Liang et al 2008;Evans et al 2009).…”

Photometric and Spectroscopic Observations of GRB 140629A

“…The joint spectral analysis of these X-ray flares with simultaneous gamma-ray pulses indicate that they are the low energy extension of the prompt gamma-ray emission . The initial steep decay phase is rather explained as being the tail emission of the last gamma-ray emission pulse due to the so-called curvature effect (e.g., Liang et al 2006;Zhang et al 2007;Mu et al 2016). Following the initial steep decay segment, XRT light curves usually have a shallow decay segment with a slope of α ∼ −0.5 or even shallower before transferring to the so-called standard decay segment with a slope of α ∼ −1.…”