Bulletin of the American Physical Society
47th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 61, Number 8
Monday–Friday, May 23–27, 2016; Providence, Rhode Island
Session C8: Invited Session: X-Ray and Inner-Shell Spectroscopy: Experiment, Theory and AstrophysicsInvited
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Chair: Tom Gorczyca, Western Michigan University Room: 555AB |
Tuesday, May 24, 2016 2:00PM - 2:30PM |
C8.00001: Precision measurements on the photoionization of neutral atomic species. Invited Speaker: Wayne Stolte In contrast to studies on rare gas atoms, experimental studies of open-shell atoms offers very challenging problems, such as creation of the atom, low signal, purity and stability. Because of this, studies of inner-shell excitations for open shell atoms are limited. In this talk I will discuss precision experimental measurements for photoionization of atomic oxygen, nitrogen, and chlorine over the last two decades on various beamlines at Lawrence Berkeley National Laboratories, Advanced Light Source. -/ References: W.C. Stolte, V. Jonauskas, D.W. Lindle, M.M. Sant'Anna, and D.W. Savin,, 2016, ApJ, accepted for publication. B.M. McLaughlin et al. 2013 ApJL, 771, L8 W.C. Stolte et al. 2013, PRA, 88, 53425 M.M. Sant'Anna, et al. 2011 PRL, 107, 33001 W.C. Stolte et al. 1997 JPB, 30, 4489 J.A.R. Samson et al. 1996 Can. J. Phys, 74, 722 [Preview Abstract] |
Tuesday, May 24, 2016 2:30PM - 3:00PM |
C8.00002: K-shell Photoioinization of the atomic nitrogen and oxygen isonuclear sequences Invited Speaker: Brendan M. McLaughlin The advent of third and fourth generation light sources, such as the ALS at Berkeley, USA, SOLEIL in Orsay, France and PETRA III in Hamburg, Germany, this past decade or more and the unprecedented high brightness and spectral resolution have made it possible to perform detailed cross section measurements in the X-ray region of extremely important astrophysical elements such as Carbon, Nitrogen and Oxygen and their isonuclear sequences [1,2,3]. In tandem with this world wide experimental endeavour theoretical work has provided interpretation in unravelling and identifying prominent resonance features in the spectra in the vicinity of the K-shell region. For the atomic oxygen sequence (K$_{\alpha}$ and K$_{\beta}$ resonance positions in the vicinity of the K-edge) we note that ground based measurements (ALS and SOLEIL) and R-matrix with pseudo-states (RMPS) theoretical results are in agreement [3,4] but are $\approx$ 0.5 eV in discrepancy with satellite observations from CHANDRA and XMM-NEWTON [5,6]. A review of the current status of experiment, theory and observation will be presented for the various sequences. \begin{enumerate} \item A. M\"uller {\it et al} PRL {114} 013002 (2015). \item M.M. Sant'Anna {\it et al} PRL {\bf 107} 033001 (2011). \item B.M. McLaughlin {\it et al} ApJL {\f 771} L8 (2013). \item J.-M. Bizau {\et al} PRA {\bf 92} 023401 (2015). \item T.W. Gorczyca {\it et al} ApJ {\bf 779} 78 (2013). \item E. Gatuzz {\it et al} ApJ {\bf 780} 80 (2013), ApJ {\bf 790} 131 (2014). \end{enumerate} [Preview Abstract] |
Tuesday, May 24, 2016 3:00PM - 3:30PM |
C8.00003: Laboratory study of K-shell photoionization of oxygen and oxygen hydrides ions Invited Speaker: Jean-Marc Bizau The interpretation of the spectra sent by satellites required the knowledge of many atomic data, including photoionization cross sections or energy and oscillator strength of bound-bound transitions for many ions, over a broad photon energy range going from infra-red to x-rays. These data are mainly provided by theoretical results using state-of-the-art methods like $R$-matrix. Recently, discrepancies have been observed between the calculated energy of the K$\alpha $ transitions in atomic oxygen and its ions and those determined from the satellites observations [1-2]. The results of the experimental studies of K-shell photoionization of oxygen ions performed at the French synchrotron radiation center SOLEIL will be presented [3]. A merged-beam setup installed on the PLEIADES beam line allows for the determination of absolute photoionization cross sections and transitions energy on singly- and multiply-charged ions in the 10-1000 eV photon energy range. The first results obtained with this setup on oxygen hydrides will be also presented. [1] E. Gatuzz et al, ApJ 768, 60 (2013) [2] F. Nicastro et al, MNRAS (2016) [3] J.M. Bizau et al, Phys Rev A 92 023401 (2015) [Preview Abstract] |
Tuesday, May 24, 2016 3:30PM - 4:00PM |
C8.00004: Astrophysical Observations of Oxygen Lines Using High-Resolution X-ray Spectra Invited Speaker: Javier Garcia Oxygen has importance in astrophysics as the most cosmically abundant element with $Z>2$. In the interstellar medium (the material between the stars in the galaxy; ISM), it is predominately found in atomic form, mostly in its neutral stage $(~90\%)$, with some fraction being singly-ionized $(~10\%)$ and doubly-ionized $(<1\%)$. This atomic oxygen produces significant absorption in the X-ray band, particularly in the form of the K-edge and the K-alpha absorption resonances of O I, O II, and O III in the 21-24 A spectral region. We have carried out a systematic study of the oxygen absorption features in the local ISM by analyzing all the high statistical quality data available from the grating instruments on the Chandra and XMM-Newton X-ray observatories. We find a clear discrepancy in the centroid wavelengths of the absorption features observed in the astrophysical data when compared with the latest laboratory measurements. In this talk, we present our current efforts to assess the absolute wavelength calibration of the instruments onboard Chandra. We discuss the need for accuracy in the atomic data for inner-shell transitions, and how accurate models for atomic absorption can contribute to understanding the ISM. [Preview Abstract] |
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