Rate Coefficients for Charge Transfer of He + with C

Kimura, Mineo; Dalgarno, A.; Chantranupong, Lek; Li, Y.; Hirsch, Gerhard; Buenker, R. J.

doi:10.1086/173361

Cited by 17 publications

(12 citation statements)

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“…Earlier calculated rate coefficients for removal of He + ( 2 S) by C or O were found to be too small to affect the ejecta models [3,6]. We note that charge exchange crosssections and rates for collisions of Si with He + were considered recently by Satta et al [32] using the multi-channel Landau-Zener approximation (MCLZ).…”

Section: Discussionmentioning

confidence: 84%

“…4, we also plot the rate coefficients for direct charge transfer from Kimura at al. [3], which become larger than the radiative charge transfer process for temperature greater than 3 000 K, approaching 7 × 10 −13 at 10 000 K.…”

Section: Resultsmentioning

confidence: 93%

“…Models of carbon monoxide formation in the ejecta of supernova SN 1987a were found to be sensitive to the description of charge transfer collisions between metal atoms and He + , but corresponding charge transfer rate coefficients were estimated due to the unavailability of measured or calculated values [1,2]. To remove this uncertainty, charge transfer cross sections and rate coefficients were calculated for C + He + [3,4] and for O + He + [5,6]. However, according to the results from this early work, the calculated values were found to be too small to affect appreciably the conclusions reached in the modelling studies.…”

Section: Introductionmentioning

confidence: 99%

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Radiative charge transfer in collisions of C with He⁺

Babb

McLaughlin

2017

J. Phys. B: At. Mol. Opt. Phys.

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Radiative charge exchange collisions between a carbon atom C( 3 P ) and a helium ion He + ( 2 S), both in their ground state, are investigated theoretically. Detailed quantum chemistry calculations are carried out to obtain potential energy curves and transition dipole matrix elements for doublet and quartet molecular states of the HeC + cation. Radiative charge transfer cross sections and rate coefficients are calculated and are found at thermal and lower energies to be large compared to those for direct charge transfer. The present results might be applicable to modelling the complex interplay of [C ii] (or C + ), C, and CO at the boundaries of interstellar photon dominated regions (PDRs) and in xray dominated regions (XDRs), where the abundance of He + affects the abundance of CO.

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Section: Discussionmentioning

confidence: 84%

Section: Resultsmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

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Radiative charge transfer in collisions of C with He⁺

Babb

McLaughlin

2017

J. Phys. B: At. Mol. Opt. Phys.

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“…we do not expect these reactions to significantly affect the atomic carbon abundance, despite the increased H + and He + abundances produced by the higher cosmic ray ionization rate. The reason for is that, in contrast to reaction 3, which proceeds at close to the Langevin rate (Anicich & Huntress 1986), reactions 4 and 5 occur only very slowly, since both have rate coefficients that are roughly a million times smaller than that of reaction 3 (Kimura et al 1993;Stancil et al 1998).…”

Section: Effect Of Varying the Cosmic Ray Ionization Ratementioning

confidence: 99%

Is atomic carbon a good tracer of molecular gas in metal-poor galaxies?

Glover

Clark

2016

Mon. Not. R. Astron. Soc.

106

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Carbon monoxide (CO) is widely used as a tracer of molecular hydrogen (H 2 ) in metalrich galaxies, but is known to become ineffective in low metallicity dwarf galaxies. Atomic carbon has been suggested as a superior tracer of H 2 in these metal-poor systems, but its suitability remains unproven. To help us to assess how well atomic carbon traces H 2 at low metallicity, we have performed a series of numerical simulations of turbulent molecular clouds that cover a wide range of different metallicities. Our simulations demonstrate that in star-forming clouds, the conversion factor between [CI] emission and H 2 mass, X CI , scales approximately as X CI ∝ Z −1 . We recover a similar scaling for the CO-to-H 2 conversion factor, X CO , but find that at this point in the evolution of the clouds, X CO is consistently smaller than X CI , by a factor of a few or more. We have also examined how X CI and X CO evolve with time. We find that X CI does not vary strongly with time, demonstrating that atomic carbon remains a good tracer of H 2 in metal-poor systems even at times significantly before the onset of star formation. On the other hand, X CO varies very strongly with time in metal-poor clouds, showing that CO does not trace H 2 well in starless clouds at low metallicity.

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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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Rate Coefficients for Charge Transfer of He + with C

Cited by 17 publications

References 0 publications

Radiative charge transfer in collisions of C with He⁺

Radiative charge transfer in collisions of C with He⁺

Is atomic carbon a good tracer of molecular gas in metal-poor galaxies?

The⁴⁴Ti-powered spectrum of SN 1987A

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Rate Coefficients for Charge Transfer of He + with C

Cited by 17 publications

References 0 publications

Radiative charge transfer in collisions of C with He+

Radiative charge transfer in collisions of C with He+

Is atomic carbon a good tracer of molecular gas in metal-poor galaxies?

The44Ti-powered spectrum of SN 1987A

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Radiative charge transfer in collisions of C with He⁺

Radiative charge transfer in collisions of C with He⁺

The⁴⁴Ti-powered spectrum of SN 1987A