Investigation of slow collisions for (quasi) symmetric heavy systems: what can be extracted from high resolution X-ray spectra

TL;DR

This study uses high-resolution X-ray spectroscopy to analyze slow symmetric heavy ion collisions, providing detailed electron capture data and benchmarking theoretical models with improved accuracy.

Contribution

The paper introduces precise measurements of electron capture probabilities and cross sections in symmetric heavy ion collisions using advanced X-ray spectroscopy techniques.

Findings

Accurate electron capture distribution ${\\mathcal{P}_n}$ determined

Benchmark data for theoretical models of electron capture

Influence of metastable state decay on hardness ratio analyzed

Abstract

We present a new experiment on (quasi) symmetric collision systems at low-velocity, namely Ar$^{17+}$ ions ($v=0.53$ a.u.) on gaseous Ar and N$_2$ targets, using low- and high-resolution X-ray spectroscopy. Thanks to an accurate efficiency calibration of the spectrometers, we extract absolute X-ray emission cross sections combining low-resolution X-ray spectroscopy and a complete determination of the ion beam - gas jet target overlap. Values with improved uncertainty are found in agreement with previous results \cite{Tawara2001}. Resolving the whole He-like Ar$^{16+}$ Lyman series from $n=2$ to 10 with our crystal spectrometer enables to determine precisely the distribution ${\mathcal{P}_n}$ of the electron capture probability and the preferential $n_{pref}$ level of the selective single-electron capture. Evaluation of cross sections for this process as well as for the contribution of multiple-capture is carried out. Their sensitivity to the $\ell$-distribution of $n$ levels populated by single-electron capture is clearly demonstrated, providing a stringent benchmark for theories. In addition, the hardness ratio is extracted and the influence of the decay of the metastable $1s2s\ ^3 S_1$ state on this ratio is discussed.