CHIANTI - An atomic database for Emission Lines. Version 8

TL;DR

The paper introduces version 8 of the CHIANTI atomic database, significantly enhancing spectral data for soft X-ray, EUV, and UV regions, with improved data assessment and format updates for better plasma modeling.

Contribution

This version adds extensive new data for ions and neutrals, updates data formats, and improves the differential emission measure computation method.

Findings

Enhanced spectral data coverage for space missions

Improved modeling capabilities for low-temperature plasma

Updated data formats for better usability

Abstract

We present version 8 of the CHIANTI database. This version includes a large amount of new data and ions, which represent a significant improvement in the soft X-ray, EUV and UV spectral regions, which several space missions currently cover. New data for neutrals and low charge states are also added. The data are assessed, but to improve the modelling of low-temperature plasma the effective collision strengths for most of the new datasets are not spline-fitted as previously, but are retained as calculated. This required a change of the format of the CHIANTI electron excitation files. The format of the energy files has also been changed. Excitation rates between all the levels are retained for most of the new datasets, so the data can in principle be used to model high-density plasma. In addition, the method for computing the differential emission measure used in the CHIANTI software has been changed.