Bulletin of the American Physical Society
43rd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 57, Number 5
Monday–Friday, June 4–8, 2012; Orange County, California
Session M3: Focus Session: Atomic Spectroscopy |
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Chair: Yuri Ralchenko, NIST Room: Grand Ballroom E |
Thursday, June 7, 2012 8:00AM - 8:30AM |
M3.00001: Resonant Auger Destruction in X-ray Photoionized Plasmas Invited Speaker: Duane Liedahl Resonant Auger Destruction (RAD) is a hypothesized line-destruction mechanism, involving the interplay of atomic kinetics and radiation transport in X-ray photoionized plasmas, and has been invoked to explain the apparent absence of K$\alpha$ satellite emission from L-shell ions in X-ray spectra of accretion-powered black holes. However, detections of this type of line emission in the X-ray spectra of neutron star accretors in our own Galaxy casts doubt on the efficacy of the RAD mechanism. Resolution of this problem, through atomic kinetics calculations, as well as direct laboratory measurements at the Sandia Z Facility, bears directly on interpretations of astrophysical X-ray spectra and accretion disk structure theory in the general relativistic domain. [Preview Abstract] |
Thursday, June 7, 2012 8:30AM - 8:42AM |
M3.00002: EUV Spectra of Xenon Observed with an Electron Beam Ion Trap Joseph Reader, Dimitry Osin, John Gillaspy, Yuri Ralchenko Extreme ultraviolet spectra of highly charged xenon atoms were produced with an electron beam ion trap (EBIT) at the National Institute of Standards and Technology (NIST) and recorded with a flat-field grazing-incidence spectrometer. The wavelength range was 4.6~nm-16.4 nm. The beam energy varied from 1.5 to 6.5 keV to selectively enhance spectra of different ionization stages. Wavelength calibration was provided by spectra of highly-charged neon, argon, and iron. Identifications of strong n=4-n=4 and n=3-n=3 transitions from Zn-like xenon (24+) to Na-like xenon (43+) were determined with the aid of collisional-radiative modeling of the EBIT plasma. Good quantitative agreement between simulated and measured spectra was achieved. Some 56 lines were identified, 48 of which are new. Seven of these lines represent magnetic dipole transitions within the 3s$^{2}$3p$^{n}$ ground configurations of these ions; one is an electric quadrupole transition within the 3s$^{2}$3p$^{2}$ ground configuration of the Si-like ion. [Preview Abstract] |
Thursday, June 7, 2012 8:42AM - 9:12AM |
M3.00003: Spectroscopy of Z-pinch plasmas: how atomic and plasma physics merge and unfold new applications Invited Speaker: Alla Safronova Recent advances in theoretical and experimental work on plasma spectroscopy of Z-pinches are presented. We have shown that the University-scale Z-pinch generators are able to produce plasmas within a broad range of temperatures, densities, opacity, and radiative properties depending on the type, geometry, size, and mass of wire array loads and wire material. The full x-ray and EUV diagnostic set for detailed spatial and temporal monitoring of such a plasma together with relativistic atomic and non-LTE kinetic codes create a very useful and productive environment for the study of atomic and plasma spectroscopy features and development of their applications. A variety of examples of K-shell low-Z (such as Mg and Al), L-shell mid-Z (such as Ni, Cu, and Ag), and M- and L-shell high-Z (W) will be considered and their specific features and applications to fusion and astrophysics will be highlighted. [Preview Abstract] |
Thursday, June 7, 2012 9:12AM - 9:24AM |
M3.00004: Synthetic X-Ray Spectra of Ar and Kr for Analysis of Data from the Z Machine at SNL Arati Dasgupta, Robert Clark, Ward Thornhill, Nicholas Ouart, John Apruzese, John Giuliani, Brent Jones, Dave Ampleford A number of shots employing concentric gas puffs of Ar and Kr on the Sandia National Laboratories ZR acceleartor are being planned, with the goal of optimizating K-shell yield. Experimental data from these implosions can provide a wealth of information about the ionization history of the plasma. Theoretical simulations using accurate atomic and hydrodynamics models will provide synthetic K-and L-shell spectra with which to compare and analyze the data. The presence and dynamics of bright K-shell emitting regions, which could possibly dominate the Kr K-shell yield, can be derived from radially and/or axially resolved, time-dependent spectra. By taking density and internal energy profiles near peak radiative power from the 2-D radiation hydrodynamics model, and post processing this data with a detailed multifrequency radiation transport scheme, the generation and evolution of these bright spots may be simulated. We will present synthetic spectra from the ``bright'' spots determined from the Ar and Kr 2D simulations, employing a recently developed non-LTE collisional-radiative spectroscopic model that combines the completeness of highly averaged Rydberg states models with the accuracy of detailed models for all important excited states. [Preview Abstract] |
Thursday, June 7, 2012 9:24AM - 9:36AM |
M3.00005: Properties of Ni$^{+}$ from microwave spectroscopy of n=9 Rydberg levels of Nickel Shannon Woods, Julie Keele, Chris Smith, Stephen Lundeen The microwave/RESIS method was used to determine the relative positions of 15 of the n=9 Rydberg levels of Nickel with L $\ge $ 6. Because the ground state of the Ni$^{+}$ ion is a $^{2}$D$_{5/2}$ level, each Rydberg level (n,L) splits into six eigenstates whose relative positions are determined by long-range e-Ni$^{+}$ interactions present in addition to the dominant Coulomb interaction. A previous study with the optical RESIS method determined these positions with precision of +/- 30 MHz [1]. Using the microwave/RESIS method improves that precision by a factor of 300, and leads to much improved determinations of the Ni+ properties that control the long-range interactions. \\[4pt] [1] Julie A. Keele, Shannon L. Woods, M.E. Hanni, and S.R. Lundeen Phys. Rev. 81, 022506 (2010) [Preview Abstract] |
Thursday, June 7, 2012 9:36AM - 9:48AM |
M3.00006: The Spectroscopy of Barium $6p_{1/2}nk$ Autoionizing States in Weak Electric Fields Jirakan Nunkaew, Thomas Gallagher We have measured the Ba $6p_{1/2}nk$, $n=17$, $5\leq k\leq n-1$ Stark autoionizing states' photoexcitation cross sections and the autoionization rates in the low field regime by isolated core excitation (ICE) of the bound Ba $6snk$ Stark states. During ICE the Rydberg electron remains in the same state ($nk$) while the ion core is excited from the ground state Ba$^+$ $6s$ to the excited state Ba$^+$ $6p_{1/2}$. However, the change in the core yields the slight change in Coulomb potential and as the result the final wavefunction of electron is different from the initial wavefunction causing the shake up of the electron to other states. We have observed the shake up of electrons from $nk$ to $nk^\prime$ states in the cross section. The observed cross section shows no transition of the electron from the $k$ state to the $k^\prime$ states on the low energy side of $k$. This is due to the fact that in low field the bound and autoionizing Stark manifolds are incomplete; they are missing the low $\ell$ states with large quantum defects. Furthermore, they are different because they contain different numbers of $\ell$ states. The cross section can be theoretically described by treating the problem as discrete states embedded in one continuum state with finite lifetime. [Preview Abstract] |
Thursday, June 7, 2012 9:48AM - 10:00AM |
M3.00007: Two-photon Direct Frequency Comb Spectroscopy of Alkali Atoms Khoa Nguyen, Trinity Pradhananga, Christopher Palm, Jason Stalnaker, Derek Jackson Kimball We are using direct frequency comb spectroscopy to study transition frequencies and excited state hyperfine structure in potassium and rubidium using 2-photon transitions excited directly with the frequency-doubled output of a erbium fiber optical frequency comb. The frequency comb output is directed in two counterpropagating directions through a vapor cell containing the atomic vapor of interest. A pair of optical filters is used to select teeth of the comb in order to identify the transition wavelengths. A photomultiplier tube (PMT) measures fluorescence from a decay channel wavelength selected with another optical filter. Using different combinations of filters enables a wide range of transitions to be investigated. By scanning the repetition rate, a Doppler-free spectrum can be obtained enabling kHz-resolution spectral measurements. The thermal motion of the atoms in the vapor cell actually eliminates the need to fine-tune the offset frequency and repetition rate, alleviating a somewhat challenging requirement for spectroscopy of cold atoms. Our investigations are laying the groundwork for a long-term research program to use direct frequency comb spectroscopy to understand the complex spectra of rare-earth atoms. [Preview Abstract] |
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