Carrera, Juan J.Chu, Shih-ITong, X. M.2023-12-072023-12-072005-06-21https://hdl.handle.net/2097/43677We present an ab initio nonpertubative investigation of the mechanisms responsible for the production of very-high-order harmonic generation (HHG) from Ar atoms and Ar+ ions by means of the self-interaction-free time-dependent density-functional theory recently developed. Further, by introducing an effective charge concept, we can study at which laser intensity the contribution to the high-energy HHG from Ar+ ions precede over the Ar atoms. Comparing the HHG behavior from Ar atoms and Ar+ ions in the superintense laser field, we conclude that the high-energy HHG observed in the recent experiment originated from the ionized Ar atoms.© American Physical Society (APS). This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).http://rightsstatements.org/vocab/InC/1.0/https://web.archive.org/web/20181120135245/https://journals.aps.org/copyrightFAQ.htmlText