Electron-impact ionization of Mg

Boivin, Robert; Srivastava, Santosh K.

doi:10.1088/0953-4075/31/10/024

Cited by 35 publications

(44 citation statements)

References 23 publications

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“…With an electron beam energy of 1 keV, one would also expect to produce and trap doubly charged ions in an observable amount [24]. The good agreement between the positions of the ions in the experiment and in the simulation presented in Fig.…”

supporting

confidence: 61%

Sympathetic Crystallization of Trapped Ions

et al. 1999

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We have created multispecies Coulomb crystals in a linear Paul trap containing up to a few hundred ions of which more than 50% were cooled only sympathetically through the Coulomb interaction with laser-cooled Mg 1 ions. In an extreme case, one laser-cooled ion maintained order in a 15 ion string. Ion species segregation was obtained by radiation pressure. Previous experiments and molecular dynamics simulations suggest the temperature is 10 mK or lower. These results indicate that a wide range of atomic and molecular ions can be cooled and localized in linear Paul traps which is important for improvements in spectroscopic studies of such ions. [S0031-9007(99)08637-8] PACS numbers: 32.80.Pj, 42.50.Vk, 52.25.Wz Trapped ions, when cooled sufficiently, form spatially ordered structures (Coulomb crystals). For smaller crystals (typically #10 5 ions), where surface effects play a dominant role, shell and stringlike structures are the equilibrium states [1-3]. Molecular dynamics (MD) simulations of infinite one component plasmas predict a body centered cubic (bcc) structure [4] as the lowest energy state. By applying laser cooling, string and shell structures have been observed in both Paul and Penning traps by imaging the fluorescence from the ions [5][6][7][8][9][10][11], and recently bcc structures at the center of very large ion crystals in a Penning trap have been revealed by Bragg scattering techniques [12,13]. Since only ions with simple level schemes accessible to lasers can easily be laser cooled, most atomic ion species, and all molecular ions, due to their complex vibrational and rotational structure, are excluded from this type of cooling. Hence, to date only very few singly charged ion species have been laser cooled and crystallized. The equations of motion in both Penning and Paul traps allow, however, ions within a certain chargeto-mass ratio to be trapped simultaneously, which makes sympathetic cooling [14] through the Coulomb interaction possible.Several authors have previously investigated sympathetic cooling, where directly laser cooled ions were used to cool ions of a different species through mutual Coulomb interaction [9,[14][15][16][17]. In most of these experiments, the typically achieved temperatures of the sympathetically cooled ions were several hundred mK, which were too high for ordering of the whole plasma. In a ring-shaped [18] and a linear Paul trap [19] a few nonfluorescing sites in crystals consisting of laser cooled 24 Mg 1 were attributed to indirectly cooled impurity ions. Recently, a crystal consisting entirely of Ca 1 was observed to stay crystallized when some of the constituent ions were decoupled from the cooling laser by being optically pumped into a metastable dark state [9].In this Letter we report on formation of Coulomb crystals consisting of up to a few hundred ions in a linear Paul trap where the fraction of indirectly (sympathetically) cooled ions is greater than 50%. In one case particularly interesting for spectroscopy, 14 sympathetically cooled ions were maintained in...

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confidence: 61%

Sympathetic Crystallization of Trapped Ions

et al. 1999

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“…It particularly takes into account charge transfer (Allan et al 1988), dielectronic recombination (Nussbaumer & Storey 1986), and electron impact ionization (Lotz 1967). The classical-empirical formula of Lotz (1967) agrees within a factor of two with the rates derived from recent measurements of the Mg electron-impact ionization cross sections (Boivin & Srivastava 1998). Rate coefficients of radiative recombination have been re-computed to incorporate new cross sections of photoionization from low-lying states of neutral Mg (Mendoza & Zeippen 1987).…”

Section: Abundances and Ionization Statementioning

confidence: 93%

High-resolution spectroscopy of flat-spectrum quasars

Tappe

Black

2004

A&A

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Abstract. We report Very Large Telescope (VLT) observations of the quasar PKS 2145+067. We obtained high-resolution (R ≈ 100 000 or 3 km s −1 ) optical spectra with the UV-Visual Echelle Spectrograph (UVES) at the VLT UT2 telescope. The emission redshift measured from [O ] is z em = 1.0003. In our spectra, the well-known intervening metal-rich absorption system at z abs = 0.79089 shows Mg  absorption lines resolved into 15 velocity components with a total spread of about 206 km s −1 . This absorption is consistent with a line of sight passing through the extended gaseous halo of a disk galaxy. The derived Doppler line broadening parameters are in the range b = 2 to 5 km s −1 . We also detected absorption lines of Mg , Fe , and Ca  in the same system. The ionization state of the absorbing gas is analyzed and compared with previous studies of PKS 2145+067. Finally, we discuss the implications of high-resolution data for proposed cosmological variations of the fine-structure constant.

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“…Similarly, for Al 1+ the increase to the single ionization cross section would be about 40%. Such large contributions might appear in the single ionization data as an inflection in the cross section at the n = 2 ionization threshold, however, such a features is not apparent in the single ionization data (Belic et al 1987;McCallion et al 1992b;Boivin & Srivastava 1998).…”

Section: Mg-likementioning

confidence: 99%

“…In order to match double ionization measurements of Mg 0+ (McCallion et al 1992b;Boivin & Srivastava 1998) and Al 1+ ) we need to increase p 0 in Equation (2) to 1.46 and 2.24, respectively, from the recommended value of 1 (Shevelko et al 2005). However, these are small corrections to the overall cross sections, which are dominated by IA.…”

Section: Mg-likementioning

confidence: 99%

Electron-impact Multiple-ionization Cross Sections for Atoms and Ions of Helium through Zinc

Hahn

Müller

Savin

2017

ApJ

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We have compiled a set of electron-impact multiple ionization (EIMI) cross sections for astrophysically relevant ions. EIMI can have a significant effect on the ionization balance of non-equilibrium plasmas. For example, it can be important if there is a rapid change in the electron temperature or if there is a non-thermal electron energy distribution, such as a kappa distribution. Cross sections for EIMI are needed in order to account for these processes in plasma modeling and for spectroscopic interpretation.Here, we describe our comparison of proposed semiempirical formulae to the available experimental EIMI cross section data. Based on this comparison, we have interpolated and extrapolated fitting parameters to systems that have not yet been measured. A tabulation of the fit parameters is provided for 3466 EIMI cross sections. We also highlight some outstanding issues that remain to be resolved.

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Electron-impact ionization of Mg

Cited by 35 publications

References 23 publications

Sympathetic Crystallization of Trapped Ions

Sympathetic Crystallization of Trapped Ions

High-resolution spectroscopy of flat-spectrum quasars

Electron-impact Multiple-ionization Cross Sections for Atoms and Ions of Helium through Zinc

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