Measurements of absolute cross sections for the photoionisation of Ba<sup>+</sup>ions

Lyon, I. C.; Peart, B; West, John B.; Dolder, K T

doi:10.1088/0022-3700/19/24/015

Cited by 107 publications

(71 citation statements)

References 14 publications

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“…Briefly, the PI cross sections were measured via the merged beam method (Lyon et al 1986). The photoionization spectra were measured by scanning across photon energies, and normalized to an absolute scale with absolute cross-section measurements performed at discrete energies.…”

Section: Comparison To Experimentsmentioning

confidence: 99%

Atomic data for neutron-capture elements

Sterling

Witthoeft

2011

A&A

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We present multi-configuration Breit-Pauli AUTOSTRUCTURE calculations of distorted-wave photoionization (PI) cross sections, and total and partial final-state resolved radiative recombination (RR) and dielectronic recombination (DR) rate coefficients for the first six ions of the trans-iron element Se. These calculations were motivated by the recent detection of Se emission lines in a large number of planetary nebulae. Se is a potentially useful tracer of neutron-capture nucleosynthesis, but accurate determinations of its abundance in photoionized nebulae have been hindered by the lack of atomic data governing its ionization balance. Our calculations were carried out in intermediate coupling with semi-relativistic radial wavefunctions. PI and recombination data were determined for levels within the ground configuration of each ion, and experimental PI cross-section measurements were used to benchmark our results. For DR, we allowed Δn = 0 core excitations, which are important at photoionized plasma temperatures. We find that DR is the dominant recombination process for each of these Se ions at temperatures representative of photoionized nebulae (∼10 4 K). In order to estimate the uncertainties of these data, we compared results from three different configuration-interaction expansions for each ion, and also tested the sensitivity of the results to the radial scaling factors in the structure calculations. We find that the internal uncertainties are typically 30-50% for the direct PI cross sections and ∼10% for the computed RR rate coefficients, while those for low-temperature DR can be considerably larger (from 15-30% up to two orders of magnitude) due to the unknown energies of near-threshold autoionization resonances. These data are available at the CDS, and fitting coefficients to the total RR and DR rate coefficients are presented. The results are suitable for incorporation into photoionization codes used to numerically simulate astrophysical nebulae, and will enable robust determinations of nebular Se abundances.

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Section: Comparison To Experimentsmentioning

confidence: 99%

Atomic data for neutron-capture elements

Sterling

Witthoeft

2011

A&A

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“…Experiments have been conducted at undulator beamline 10.0 at the ALS, using the ion-photon merged-beams end station [1,2] shown schematically in Fig 1. The technique was developed by Lyon and coworkers [3], and has been recently employed by Kjeldsen et al [4] and others [5]. An energy selected photon beam is merged over a path length of approximately one meter with an ion beam produced by an ECR ion source and a small accelerator.…”

Section: Methodsmentioning

confidence: 99%

Photoionization of Multiply Charged Ions at the Advanced Light Source

Schlachter¹,

Kilcoyne²,

Aguilar³

et al. 2005

AIP Conference Proceedings

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Abstract. Photoionization of multiply charged ions is studied using the merged-beams technique at the Advanced Light Source. An ion beam is created using a compact 10-GHz all-permanent-magnet ECR ion source and is accelerated with a small accelerator. The ion beam is merged with a photon beam from an undulator to allow interaction over an extended path. Absolute photoionization cross sections have been measured for a variety of ions along both isoelectronic and isonuclear sequences.

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“…Earlier set-ups for ion spectroscopy at synchrotron facility were based on merged beam experiments in which ion beams of high current were merged over tenth of centimeter and up to one meter with monochromatic synchrotron radiation [10]. Excellent sensitivity has been achieved and cross sections of below the Mbarn are within reach.…”

Section: Experimental Set-upmentioning

confidence: 99%