Experimental measurement of state-selective charge exchange and test of astrophysics soft X-ray emission model

doi:10.7498/aps.70.20201685

	Experimental measurement of state-selective charge exchange and test of astrophysics soft X-ray emission model
	Xu Jia-Wei 3,5; Xu Chuan-Xi 1,4,5; Zhang Rui-Tian 3,5; Zhu Xiao-Long 3,5; Feng Wen-Tian 5; Zhao Dong-Mei 5; Liana Gui-Yun 2; Guo Da-Long 5; Gao Yong 5; Zhang Shao-Feng 3,5
刊名	ACTA PHYSICA SINICA
	2021-04-20
卷号	70 期号:8 页码:8
关键词	reaction microscopes charge exchange state selective capture soft X-ray
ISSN号	1000-3290
DOI	10.7498/aps.70.20201685
通讯作者	Zhu Xiao-Long(zhuxiaolong@impcas.ac.cn) ; Ma Xin-Wen(x.ma@impcas.ac.cn)
英文摘要	Charge exchange, or electron capture, between highly charged ions and atoms and molecules has been considered as one of important mechanisms controlling soft X-ray emissions in many astrophysical objects and environments. However, to model charge exchange soft X-ray emission, astrophysicists commonly use principal quantum number n and angular momentum quantum numberl resolved state-selective capture cross section data, which are usually obtained by empirical and semi-classical theory calculations. The accuracy of the theoretical model is the key to constructing an accurate X-ray spectrum. With a newly-built cold target recoil ion momentum spectroscopy apparatus, we perform a series of precise state-selective cross section measurements on Ne8+ ions' single electron capture with He targets, with the projectile energy ranging from 1.4 to 20 keV/u. The experimentally measured Q value spectrum shows that the process of electron captured to state of Ne7+ with n = 4 is the main reaction channel, and that with n = 3 and 5 are the small reaction channels. Using Gaussian curve to fit the area of each channel on the Q value spectrum and normalizing the area of all channels, we obtain the n-resolved relative state-selective cross section. By comparing the measured relative cross sections with the results calculated by the multichannel Landau-Zener method and molecular Coulomb over-barrier model, significant difference among the strengths of small reaction channels is found. Specifically, the multichannel Landau-Zener method overestimates the contribution of n = 2 channel and n = 3 channel, and underestimates the contribution of n = 5 channel. The molecular Coulomb over-barrier model overestimates the contribution of n = 5 channel and underestimates the contribution of n = 3 channel. The significant difference between the theoretical model calculation and experimental measurement is due to the limitations of semiclassical theoretical method and classical theoretical method. Furthermore, with l distribution models commonly used in the astrophysical literature, including the statistical model, separable model, Landau-Zener-I model, Landau-Zener-II model and even model, we calculate the soft X-ray emissions in the charge exchange between 1.6 and 2.4 keV/u Ne8+ and He. It is found that the calculated intensities of X-ray spectra significantly deviate from the existing measurements, and only the separable model can partly match the laboratory simulated solar wind charge exchange X-ray measurement. Furthermore, we find that the intensity of the charge exchange X-ray emission spectrum measured experimentally is dependent on the collision energy, while the emission spectrum calculated based on the model seems to be unchanged with the increase of the collision energy. These results indicate that if the classical and semi-classical models are applied to the astrophysical plasma for studying diffusive soft X-ray background, the obtained parameters of the astrophysical plasma will be inaccurate.
资助项目	State Key R&D Program of China[2017YFA0402400] ; State Key R&D Program of China[2017YFA0402300] ; Strategic Leading Science and Technology Project of Chinese Academy of Sciences[XDB34020000]
WOS关键词	ION-MOMENTUM SPECTROSCOPY ; SINGLE-ELECTRON CAPTURE ; SOLAR-WIND ; RECOIL-ION ; SLOW COLLISIONS ; NE-8+ ; O-8+ ; O-7+ ; HE
WOS研究方向	Physics
语种	英语
出版者	CHINESE PHYSICAL SOC
WOS记录号	WOS:000643680000004
资助机构	State Key R&D Program of China ; Strategic Leading Science and Technology Project of Chinese Academy of Sciences
内容类型	期刊论文
源URL	[http://119.78.100.186/handle/113462/137534]
专题	中国科学院近代物理研究所
通讯作者	Zhu Xiao-Long; Ma Xin-Wen
作者单位	1.Northwest Normal Univ, Joint Lab Atom & Mol Phys Extreme Environm, Lanzhou 730000, Peoples R China 2.Chinese Acad Sci, Natl Astron Observ, Key Lab Opt Astron, Beijing 100084, Peoples R China 3.Univ Chinese Acad Sci, Beijing 100084, Peoples R China 4.Northwest Normal Univ, Coll Phys & Elect Engn, Key Lab Atom & Mol Phys & Funct Mat Gansu Prov, Lanzhou 730000, Peoples R China 5.Chinese Acad Sci, Inst Modern Phys, Lanzhou 730000, Peoples R China
推荐引用方式 GB/T 7714	Xu Jia-Wei,Xu Chuan-Xi,Zhang Rui-Tian,et al. Experimental measurement of state-selective charge exchange and test of astrophysics soft X-ray emission model[J]. ACTA PHYSICA SINICA,2021,70(8):8.
APA	Xu Jia-Wei.,Xu Chuan-Xi.,Zhang Rui-Tian.,Zhu Xiao-Long.,Feng Wen-Tian.,...&Ma Xin-Wen.(2021).Experimental measurement of state-selective charge exchange and test of astrophysics soft X-ray emission model.ACTA PHYSICA SINICA,70(8),8.
MLA	Xu Jia-Wei,et al."Experimental measurement of state-selective charge exchange and test of astrophysics soft X-ray emission model".ACTA PHYSICA SINICA 70.8(2021):8.