Abstract
Measurements of the single photoionization cross section of Cu-like Zn$^+$ ions are reported in the energy (wavelength) range 17.5 eV (709 \AA) to 90 eV (138 \AA). The measurements on this {\it trans}-Fe element were performed at the Advanced Light Source synchrotron radiation facility in Berkeley, California at a photon energy resolution of 17 meV using the photon-ion merged-beams end-station. Below 30 eV the spectrum is dominated by excitation autoionizing resonance states. The experimental results are compared with large-scale photoionization cross-section calculations performed using a Dirac-Coulomb $R$-matrix approximation. Comparison are made with previous experimental studies, resonance states are identified and contributions from metastable states of Zn$^+$ determined.
Highlights
About half of the heavy elements (Z ≥30) in the Universe were formed during the Asymptotic Giant Branch (AGB) phase through slow neutron-capture (n-capture) nucleosynthesis
Photoionization cross sections producing Zn2+ from Zn+ ions were measured in the photon energy range of 17.5 eV – 90 eV with a photon energy resolution of 17 meV FWHM
All the sharp resonance features present in the spectrum have been analyzed and identified. These resonance features we attribute to Rydberg transitions originating from the ground state Zn+ into excited autoionizing states of the Zn+ ion that ionize to the different 3d94s 3D3,2,1 and 3d94s 1D2 threshold states of Zn2+
Summary
About half of the heavy elements (Z ≥30) in the Universe were formed during the Asymptotic Giant Branch (AGB) phase through slow neutron-capture (n-capture) nucleosynthesis (the s-process). The chemical composition of these objects illuminate de- Atomic data, such as PI cross sections, are unknown for the vast majority of trans-Fe, neutron-capture element ions. Measuring the abundances of these elements helps to reveal their dominant production sites in the Universe, as well as details of stellar structure, mixing and nucleosynthesis (Sharpee et al 2007; Langanke & Wiescher 2001; Sterling et al 2016) These astrophysical observations are the motivation to determine the EIE, EII, PI, and recombination properties of n-capture elements (Cardelli et al 1993; Smith & Lambert 2015; Wallerstein et al 1997; Busso et al 1999; Langanke & Wiescher 2001; Travaglio et al 2004; Herwig 2005; Cowan & Sneden 2006). A comparison of the darc PI cross sections with previous experimental studies (Peart et al 1987) and the present ALS work indicate excellent agreement, providing further confidence in the data for various astrophysical applications
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