Branching Processes in the Dissociative Recombination of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msubsup><mml:mrow><mml:mi mathvariant="normal">H</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msubsup></mml:mrow></mml:math>

Datz, S.; Sundström, Gerdt; Biedermann, C.; Broström, L.; Danared, H.; Mannervik, S.; Mowat, J. R.; Larsson, Mats

doi:10.1103/physrevlett.74.4099.2

Cited by 15 publications

(17 citation statements)

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“…We treat the low-energy collision process as a curve-crossing problem, which was previously thought inapplicable 20 to low-energy recombination in H + 3 . Our calculation reproduces the measured propensity for three-body versus two-body breakup of the neutral fragments 3 , as well as the vibrational distribution 4 of the H 2 product molecules.…”

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confidence: 55%

Mechanism for the destruction of H3+ ions by electron impact

Kokoouline

Greene

Esry

2001

Nature

172

147

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The rate at which the simplest triatomic ion (H+3) dissociates following recombination with a low-energy electron has been measured in numerous experiments. This process is particularly important for understanding observations of H+3 in diffuse interstellar clouds. But, despite extensive efforts, no theoretical treatment has yet proved capable of predicting the measured dissociative recombination rates at low energy, even to within an order of magnitude. Here we show that the Jahn-Teller symmetry-distortion effect-almost universally neglected in the theoretical description of electron-molecule collisions-generates recombination at a much faster rate than any other known mechanism. Our estimated rate constant overlaps the range of values spanned by experiments. We treat the low-energy collision process as a curve-crossing problem, which was previously thought inapplicable to low-energy recombination in H+3. Our calculation reproduces the measured propensity for three-body versus two-body breakup of the neutral fragments, as well as the vibrational distribution of the H2 product molecules.

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confidence: 55%

Mechanism for the destruction of H3+ ions by electron impact

Kokoouline

Greene

Esry

2001

Nature

172

147

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“…de Kok et al 2013;Brogi et al 2012). Based on our model predictions for H + 3 emissions, we estimate the planetary emission to stellar continuum contrast to be approximately 7 × 10 −7 for a planet at 0.2 AU from a star similar to AD Leo, dropping to 3 × 10 −8 at 1 AU from the same star.…”

Section: Emissionsmentioning

confidence: 99%

“…The difficulties are further compounded by the relatively small number of H + 3 emission lines (of the order of tens rather than thousands as in the case of CO absorption lines) that does not lead to the same gain in the crosscorrelations. Furthermore, simulations by de Kok et al (2013) suggested that signatures from emission lines might be more difficult to retrieve than from absorption lines (see their Fig. 5).…”

Section: Emissionsmentioning

confidence: 99%

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EUV-driven ionospheres and electron transport on extrasolar giant planets orbiting active stars

Chadney

Galand

Koskinen

et al. 2016

A&A

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The composition and structure of the upper atmospheres of extrasolar giant planets (EGPs) are affected by the high-energy spectrum of their host stars from soft X-rays to the extreme ultraviolet (EUV). This emission depends on the activity level of the star, which is primarily determined by its age. In this study, we focus upon EGPs orbiting K-and M-dwarf stars of different ages -Eridani, AD Leonis, AU Microscopii -and the Sun. X-ray and EUV (XUV) spectra for these stars are constructed using a coronal model. These spectra are used to drive both a thermospheric model and an ionospheric model, providing densities of neutral and ion species. Ionisation -as a result of stellar radiation deposition -is included through photo-ionisation and electron-impact processes. The former is calculated by solving the Lambert-Beer law, while the latter is calculated from a supra-thermal electron transport model. We find that EGP ionospheres at all orbital distances considered (0.1−1 AU) and around all stars selected are dominated by the long-lived H + ion. In addition, planets with upper atmospheres where H 2 is not substantially dissociated (at large orbital distances) have a layer in which H + 3 is the major ion at the base of the ionosphere. For fast-rotating planets, densities of short-lived H + 3 undergo significant diurnal variations, with the maximum value being driven by the stellar X-ray flux. In contrast, densities of longer-lived H + show very little day/night variability and the magnitude is driven by the level of stellar EUV flux. The H + 3 peak in EGPs with upper atmospheres where H 2 is dissociated (orbiting close to their star) under strong stellar illumination is pushed to altitudes below the homopause, where this ion is likely to be destroyed through reactions with heavy species (e.g. hydrocarbons, water). The inclusion of secondary ionisation processes produces significantly enhanced ion and electron densities at altitudes below the main EUV ionisation peak, as compared to models that do not include electron-impact ionisation. We estimate infrared emissions from H + 3 , and while, in an H/H 2 /He atmosphere, these are larger from planets orbiting close to more active stars, they still appear too low to be detected with current observatories.

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“…Moreover, observation of four-body break-up was reported, though it was not a dominant channel [12]. A systematic investigation into the fragmentation of XH 2 + ions (X=H, C, N, O and P) has revealed a propensity for the three-body break-up [13][14][15][16][17]. To shed more light on the DR fragmentation of XH …”

Section: Introductionmentioning

confidence: 99%