A Kinetic Database for Astrochemistry (Kida)

Wakelam, Valentine; Herbst, Eric; Loison, Jean‐Christophe; Smith, Ian W. M.; Chandrasekaran, Vijayanand; Pavone, B.; Adams, Nigel G.; Bacchus‐Montabonel, Marie‐Christine; Bergeat, Astrid; Béroff, K.; Bierbaum, Veronica M.; Chabot, M.; Dalgarno, A.; Dishoeck, E. F. van; Faure, A.; Geppert, Wolf D.; Gerlich, D.; Galli, Daniele; Hébrard, Éric; Hersant, F.; Hickson, Kevin M.; Honvault, Pascal; Klippenstein, Stephen J.; Picard, S.; Nyman, Gunnar; Pernot, Pascal; Schlemmer, S.; Selsis, F.; Sims, Ian; Talbi, Dahbia; Tennyson, Jonathan; Troe, J.; Wester, Roland; Wiesenfeld, Laurent

doi:10.1088/0067-0049/199/1/21

Cited by 507 publications

(478 citation statements)

References 139 publications

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“…However, we show in Appendix C how the (isotope-free) chemistry of the main species discussed later in this paper changes for three different chemical sets. For a similar discussion see also Wakelam et al (2012).…”

Section: Choice Of the Chemical Data Setmentioning

confidence: 72%

Carbon fractionation in photo-dissociation regions

Röllig

Ossenkopf

2013

A&A

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We upgraded the chemical network from the UMIST Database for Astrochemistry 2006 to include isotopes such as 13 C and 18 O. This includes all corresponding isotopologues, their chemical reactions and the properly scaled reaction rate coefficients. We study the fractionation behavior of astrochemically relevant species over a wide range of model parameters, relevant for modelling of photo-dissociation regions (PDRs). We separately analyze the fractionation of the local abundances, fractionation of the total column densities, and fractionation visible in the emission line ratios. We find that strong C + fractionation is possible in cool C + gas. Optical thickness as well as excitation effects produce intensity ratios between 40 and 400. The fractionation of CO in PDRs is significantly different from the diffuse interstellar medium. PDR model results never show a fractionation ratio of the CO column density larger than the elemental ratio. Isotope-selective photo-dissociation is always dominated by the isotope-selective chemistry in dense PDR gas. The fractionation of C, CH, CH + and HCO + is studied in detail, showing that the fractionation of C, CH and CH + is dominated by the fractionation of their parental species. The light hydrides chemically derive from C + , and, consequently, their fractionation state is coupled to that of C + . The fractionation of C is a mixed case depending on whether formation from CO or HCO + dominates. Ratios of the emission lines of [C ii], [C i], 13 CO, and H 13 CO + provide individual diagnostics to the fractionation status of C + , C, and CO.

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Section: Choice Of the Chemical Data Setmentioning

confidence: 72%

Carbon fractionation in photo-dissociation regions

Röllig

Ossenkopf

2013

A&A

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“…We calculate the branching ratio using RRKM theory, leading mainly to C + HCN product with a small contribution from H + CNC, and the global rate constant has been calculated using capture theory leading to k C+HCN = 210 -10 cm 3 molecule -1 s -1 in the 10-300 K range. (Wakelam et al 2012 et al 1996) N + C2H3 +  HC2N + + H2 2.2e-10 0 0 3.0 0 (Federer et al 1986) N + C2H4 +  CH2CNH + + H 3.0e-10 0 0 1.8 0 (Scott et al 1999 (Stief et al 1995, Yang et al 2005b Estimation using (Fikri et al 2001, Zhang et al 2004. HCNO is likely produced but is not in our model.…”

Section: + Hncmentioning

confidence: 82%

The interstellar gas-phase chemistry of HCN and HNC

Loison¹,

Wakelam²,

Hickson³

2014

Monthly Notices of the Royal Astronomical Society

107

109

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+ CH 2 reaction and two new reactions: H + CCN and C + HNC. We test the effect of the new rate constants and branching ratios on the predictions of gas-grain chemical models for dark cloud conditions. The rapid C + HNC reaction keeps the HCN/HNC ratio significantly above one as long as the carbon atom abundance remains high. However, the reaction of HCN with H 3 + followed by DR of HCNH + acts to isomerize HCN into HNC when carbon atoms and CO are depleted leading to a HCN/HNC ratio close to or slightly greater than 1. This agrees well with observations in TMC-1 and L134N taking into consideration the overestimation of HNC abundances through the use of the same rotational excitation rate constants for HNC as for HCN in many radiative transfer models.

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“…This result can have implications for chemical networks because they assume statistical weights for the three products CO, HCO, and H 2 CO (1/3, 1/3, 1/3), as in the UMIST12 network or the KIDA 3 database (Wakelam et al 2012), following Prasad & Huntress (1980). As already noted in Hamberg et al (2007), these branching ratios are still vastly in agreement with their experimental results, which state that CO, HCO and H 2 CO represent over 90% of the products.…”

Section: Discussionmentioning

confidence: 99%

Detection of protonated formaldehyde in the prestellar core L1689B

Bacmann

García-García

Fauré

2016

A&A

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Complex organic molecules (COMs) are detected in many regions of the interstellar medium, including prestellar cores. However, their formation mechanisms in cold (∼10 K) cores remain to this date poorly understood. The formyl radical HCO is an important candidate precursor for several O-bearing terrestrial COMs in cores, as an abundant building block of many of these molecules. Several chemical routes have been proposed to account for its formation: on grain surfaces, as an incompletely hydrogenated product of H addition to frozen-out CO molecules; and in the gas phase, either as the product of the reaction between H 2 CO and a radical or as a product of dissociative recombination of protonated formaldehyde H 2 COH + . The detection and abundance determination of H 2 COH + , if present, could provide clues as to whether this latter scenario might apply. We searched for protonated formaldehyde H 2 COH + in the prestellar core L1689B using the IRAM 30 m telescope. The H 2 COH + ion is unambiguously detected, for the first time, in a cold (∼10 K) source. The derived abundance agrees with a scenario in which the formation of H 2 COH + results from the protonation of formaldehyde. We use this abundance value to constrain the branching ratio of the dissociative recombination of H 2 COH + towards the HCO channel to ∼10−30%. This value could however be lower if HCO were efficiently formed from neutralneutral reactions in the gas phase, and we stress the need for laboratory measurements of the rate constants of these reactions at 10 K. Given the experimental difficulties in measuring branching ratios experimentally, observations can place valuable constraints on these values and provide useful input for chemical networks.

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A Kinetic Database for Astrochemistry (Kida)

Cited by 507 publications

References 139 publications

Carbon fractionation in photo-dissociation regions

Carbon fractionation in photo-dissociation regions

The interstellar gas-phase chemistry of HCN and HNC

Detection of protonated formaldehyde in the prestellar core L1689B

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