Precision spectroscopy and electron-ion scattering

Abstract

Scientific research fields for future source of energy such as inertial confinement fusion research and astrophysics studies, especially with satellite observatories, advance into stages of precision physics. The relevant atomic data are not only enormous but also of accuracy according to requirements, especially for both energy levels and the collision data. We propose a scenario to provide such abundant atomic data with enough accuracy based on analytical continuation properties of the scattering matrices, which is a combination of indispensable theoretical computations and benchmark experimental measurements. Using our modified R-matrix method we can directly calculate the scattering matrices in the whole energy regions, from which we can obtain all energy levels and the related scattering cross sections with accuracies comparable with spectroscopic precision. The e+Kr + system is used as an illustrative example; the degrees of accuracies of scattering matrices of each partial wave are calculated within about 6%, which should be much more accurate than state-of-the-art scattering experiments.

Change of the relative line strengths due to the resonance induced population transfer between Fe XVII and FeXVI ions

“…All required transition rates between 810 eV and 830 eV for the Fe XVII ions have already been obtained from the extended MCDF calculation discussed earlier. For the Fe XVI ion, the transition rates are calculated with the well-established atomic structure theories such as the relativistic eigenchannel R-matrix method detailed elsewhere 20,32 . In particular, for the autoionization rate, our calculation has taken into account fully the interaction between various resonant states and the continua.…”

On the consistent use of scale variations in PDF fits and predictions

“…The eventual interpretation of these results has the potential to be a matter of some debate, given the known issues with the 'rule of thumb' scale variation approach and availability of alternative, potentially superior, approaches (see for example [36][37][38]). Nonetheless the initial investigations of the inclusion of theoretical uncertainties in PDF fits currently apply the scale variation paradigm [25,33,39], and so this result is certainly directly relevant to these studies. Thus, one is free to apply a potentially more complete and reliable approach than scale variation to evaluating the theoretical uncertainty due to missing higher orders in the PDF fit.…”

Interaction between overlapping doubly excited resonance series for the He atom

“…These wave functions are connected by the R-matrix defined on their common boundary, i.e., at r = r o . Recently, Gao and Li have extended both the non-relativistic and relativistic versions of the eigenchannel R-matrix method, referred to as R-eigen and R-R-eigen, respectively [15,16], from the earlier Breit-Pauli [19] and Dirac R-matrix codes [20]. With the ECR method, we are able to obtain the scattering matrices corresponding to the physical parameters associated with the multichannel quantum defect theory (MQDT) [22][23][24][25] for both the discrete and continuous energy regions of interest.…”

“…We will also demonstrate in details the level crossing between overlapping resonance series and how they migrate due to the interaction between series. Our discussions are based on the theoretical spectra derived from two distinct theoretical approaches, the B-spline-based K-matrix (BSK) method [14] and the eigenchannel R-matrix (ECR) method [15,16]. One important advantage we enjoy in our present study is the ability to compare the theoretical results from these two different calculations.…”