Charge Transfer in Collisions of C<sup>+</sup>with H and H<sup>+</sup>with C

Stancil, P. C.; Havener, C. C.; Krstić, Predrag; Schultz, David; Kimura, Mineo; Gu, Jie; Hirsch, Gerhard; Buenker, Robert J.; Zygelman, B.

doi:10.1086/305937

Cited by 47 publications

(35 citation statements)

References 27 publications

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“…We use charge transfer rates taken from Rutherford et al (1971), Rutherford et al (1972), Arnaud & Rothenflug (1985), Pequignot & Aldrovandi (1986), Kimura et al (1993), Swartz (1994), Kingdon & Ferland (1996), Stancil et al (1998) and Zhao et al (2004). For reactions where no measured or calculated rates exist, we use the recipe for estimating rates given by Pequignot & Aldrovandi (1986).…”

Section: Charge Transfermentioning

confidence: 99%

The⁴⁴Ti-powered spectrum of SN 1987A

Jerkstrand

Fransson

Kozma

2011

A&A

172

249

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SN 1987A provides a unique opportunity to study the evolution of a supernova from explosion into very late phases. Owing to the rich chemical structure, the multitude of physical processes involved and extensive radiative transfer effects, detailed modeling is needed to interpret the emission from this and other supernovae. In this paper, we analyze the late-time (about eight years) Hubble Space Telescope spectrum of the SN 1987A ejecta, where 44 Ti is the dominant power source. Based on an explosion model for a 19 M progenitor, we compute a model spectrum by calculating the degradation of positrons and gamma-rays from the radioactive decays, solving the equations governing temperature, ionization balance and NLTE level populations, and treating the radiative transfer with a Monte Carlo technique. We obtain a UV/optical/NIR model spectrum that reproduces most of the lines in the observed spectrum with good accuracy. We find non-local radiative transfer in atomic lines to be an important process also at this late stage of the supernova, with ∼30% of the emerging flux in the optical and NIR coming from scattering/fluorescence. We investigate the question of where the positrons deposit their energy, and favor the scenario where they are locally trapped in the Fe/He clumps by a magnetic field. Energy deposition into these largely neutral Fe/He clumps makes Fe I lines prominent in the emerging spectrum. With the best available estimates for the dust extinction, we determine the amount of 44 Ti produced in the explosion to be 1.5 +0.5 −0.5 × 10 −4 M .

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Section: Charge Transfermentioning

confidence: 99%

The⁴⁴Ti-powered spectrum of SN 1987A

Jerkstrand

Fransson

Kozma

2011

A&A

172

249

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“…We consider here the evolution of the following carbon species: C, C + , C − , CH, CH + , CH 2 and CH + 2 . The reaction rates are taken from the umist database (Woodall et al 2007), except for five reactions: reaction C7 ), the two charge transfers C8 and C9 between C, H and their respective ions (Stancil et al 1998a), the recombination C48 (Omukai 2000) and the photoionisation C49, whose cross section is taken from Verner et al (1996, see Table A.5 of the Appendix). The main reaction leading to the synthesis of CH is clearly the radiative association C15 (C + H → CH + γ), but we also include the neutral reaction C12 and the two associative detachments C17 and C27.…”

Section: Carbonmentioning

confidence: 99%

Chemistry of heavy elements in the Dark Ages

Vonlanthen¹,

Rauscher

Winteler

et al. 2009

A&A

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Context. Primordial molecules were formed during the Dark Ages, i.e. the time between recombination and reionization in the early Universe. They were the constituents of the first proto-stellar clouds. Standard Big Bang nucleosynthesis predicts the abundances of hydrogen, helium, lithium, beryllium, and their isotopes in the early Universe. Heavier nuclei such as carbon, nitrogen, or oxygen are only formed in trace amounts. In nonstandard Big Bang nucleosynthesis models, it is possible to synthesize greater quantities of these heavier elements. The latter are interesting because they can form molecules with a high electric dipole moment which can increase the cooling in collapsing protostellar structures. Aims. The purpose of this article is to analyze the formation of primordial molecules based on heavy elements during the Dark Ages, with elemental abundances taken from different nucleosynthesis models. Methods. We present calculations of the full nonlinear equation set governing the primordial chemistry. We considered the evolution of 45 chemical species and used an implicit multistep method of variable order of precision with an adaptive stepsize control. Results. The cosmological recombination of heavy elements is presented for the first time. We find that the most abundant Dark Age molecules based on heavy elements are CH and OH. When considering initial conditions given by the standard Big Bang nucleosynthesis model, we obtain relative abundances [CH] = n CH /n b = 6.2 × 10 −21 and [OH] = n OH /n b = 1.2 × 10 −23 at z = 10, where n b is the total number density. But nonstandard nucleosynthesis can lead to higher heavy element abundances, while still satisfying the observed primordial light abundances. In that case, we show that the abundances of molecular species based on C, N, O, and F can be enhanced by two orders of magnitude, leading to a CH relative abundance higher than that of HD + or H 2 D + .

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“…For transitions for which data were not available, we incorporated the formulation of Seaton (1962). Charge exchange rates with protons were obtained from Stancil et al (1998aStancil et al ( , 1998b, Lin et al (2005), and Stancil et al (1999), for C, N, and O, respectively. Collisional excitation and ionization by neutral H was assumed according to Kaulakys (1985) formula for Rydberg levels and neglected for lower levels.…”

Section: The C and O Nlte Calculationsmentioning

confidence: 99%

Semiempirical Models of the Solar Atmosphere. II. The Quiet‐Sun Low Chromosphere at Moderate Resolution

Fontenla

Balasubramaniam

Harder

2007

ApJ

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We present a new, one-dimensional model of the solar atmosphere (called SRPM 305) at moderate angular resolution ($1 00 Y2 00 ). Key characteristics of the SRPM 305 model include (1) a minimum temperature of $3800 K at a gas pressure of $80 dyne cm À2 and (2) a rapid temperature rise above the temperature-minimum layer that results in substantial overionization of most elements when compared with LTE calculations. The model calculations reproduce the $4300 K minimum brightness temperature of the UV continuum ( between 1400Y1500 8) observed by SUMER and the $4400 K observed minimum radio-continuum brightness temperature (between wavelengths 0.01 and 100 mm). Neither the UV nor the radio continuum bear on the low-temperature minimum value because their broad intensity contribution functions cause the higher temperatures of the upper chromospheric layers to effectively hide the low minimum temperature region. The SRPM 305 model reproduces the observed intensities of CO lines at 4.466 m, at both the disk center and near the limb, by using C and O abundances consistent with recent literature low values. The model also reproduces observed intensities of C i spectral lines at 5381 and 8337 8, CH lines at about 4306 8, the CN band head at 3883 8, and the O i lines at 7772, 7774, and 7776 8, respectively. Using the SRPM 305 model, we find no significant abundance variations between the photosphere and the low chromosphere. Consequently, the single-component model presented here matches several apparently contradictory observations and thereby resolves the controversy about the temperature minimum value.

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Charge Transfer in Collisions of C⁺with H and H⁺with C

Cited by 47 publications

References 27 publications

The⁴⁴Ti-powered spectrum of SN 1987A

The⁴⁴Ti-powered spectrum of SN 1987A

Chemistry of heavy elements in the Dark Ages

Semiempirical Models of the Solar Atmosphere. II. The Quiet‐Sun Low Chromosphere at Moderate Resolution

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Charge Transfer in Collisions of C+with H and H+with C

Cited by 47 publications

References 27 publications

The44Ti-powered spectrum of SN 1987A

The44Ti-powered spectrum of SN 1987A

Chemistry of heavy elements in the Dark Ages

Semiempirical Models of the Solar Atmosphere. II. The Quiet‐Sun Low Chromosphere at Moderate Resolution

Contact Info

Product

Resources

About

Charge Transfer in Collisions of C⁺with H and H⁺with C

The⁴⁴Ti-powered spectrum of SN 1987A

The⁴⁴Ti-powered spectrum of SN 1987A