Presentation Type

Poster

Abstract

Elements heavier than iron, or trans-iron elements, are increasingly important to astronomers. Spectroscopic measurements reveal that these heavy elements are present in planetary nebulae (gaseous clouds that surround dying stars). From these spectra, astronomers can calculate elemental abundances that are then used to determine the chemical composition of the parent star. Accurate determinations of these elemental abundances are critical to theoretical models of stellar nucleosynthesis and our understanding of the chemical evolution of the Universe.

In order to calculate elemental abundances, astronomers first need to identify which elements’ spectroscopic profiles are present in their measurements. They do so by comparing their observations to high-energy-resolution photoionization spectra measured by our research group. Our team of atomic physicists measures the absolute photoionization cross-sections for these elements at the Advanced Light Source, a third-generation synchrotron radiation source located at Lawrence Berkeley National Laboratory. To produce the required spectra we merge the element under consideration with intense beams of ultraviolet or x-ray radiation and collect the ions produced as a function of photon energy.

This analysis focuses on photoionization cross-sections for Xe+ and Xe2+ and includes a discussion on interesting features like Rydberg series and window resonances.

Category

Physical Sciences

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Apr 11th, 11:00 AM Apr 11th, 12:00 PM

Absolute Photoionization Cross-Sections for Xe+ and Xe2+

Elements heavier than iron, or trans-iron elements, are increasingly important to astronomers. Spectroscopic measurements reveal that these heavy elements are present in planetary nebulae (gaseous clouds that surround dying stars). From these spectra, astronomers can calculate elemental abundances that are then used to determine the chemical composition of the parent star. Accurate determinations of these elemental abundances are critical to theoretical models of stellar nucleosynthesis and our understanding of the chemical evolution of the Universe.

In order to calculate elemental abundances, astronomers first need to identify which elements’ spectroscopic profiles are present in their measurements. They do so by comparing their observations to high-energy-resolution photoionization spectra measured by our research group. Our team of atomic physicists measures the absolute photoionization cross-sections for these elements at the Advanced Light Source, a third-generation synchrotron radiation source located at Lawrence Berkeley National Laboratory. To produce the required spectra we merge the element under consideration with intense beams of ultraviolet or x-ray radiation and collect the ions produced as a function of photon energy.

This analysis focuses on photoionization cross-sections for Xe+ and Xe2+ and includes a discussion on interesting features like Rydberg series and window resonances.