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What is KIDA ?
KIDA (for KInetic Database for Astrochemistry) is a project initiated by different communities in order to 1) improve the interaction between astrochemists and physico-chemists and 2) simplify the work of modeling the chemistry of astrophysical environments. Here astrophysical environments stand for the interstellar medium and planetary atmospheres. Both types of environments use similar chemical networks and the physico-chemists who work on the determination of reaction rate coefficients for both types of environment are the same.
For the interstellar medium, we provide chemical reactions occuring the gas-phase but also some parameters used to compute the interaction of species with the surface of interstellar grains and the chemical reactions occuring at the surface of these grains. We refer to Wakelam et al. (2010) and reference therein for a description of these processes. The types of data that are stored in KIDA are described here.
In KIDA, you can find different values for the same parameters from different bibliographic sources. In some cases, a quality indicator is also present. In addition to these reactions several chemical networks (a selection of reactions) specific for some astronomical objects are available. They can be directly from KIDA or compiled by users.

The KIDA database has been presented in the following scientific paper:
Wakelam et al. The Astrophysical Journal Supplement, Volume 199, Issue 1, article id. 21, 10 pp. (2012)
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What type of data can I find in KIDA?
The following type of data can be found:
  • Gas-phase reactions and associated partial rate coefficients (with detailed information)
  • Polarizability, dipole moment and enthalpy of formation for some species.
  • Desorption energies (from different types of surfaces) and diffusion energies (on different types of surfaces) for some species.
  • Chemical reactions occuring at the surface of interstellar grains with branching ratios, activation energies and barrier width.
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What can you do in KIDA?
  • You can find all existing data useful for the chemical modeling of interstellar chemistry and planetary atmospheres with detailed information.
  • You can add data (reactions, rate coefficients, desorption energy, diffusion energy) to the database through csv templates.
  • You can download a complete set of reaction rate coefficients and/or store your list of reactions.
  • You can find information on the quality of the data and recommanded data for some of them.
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Who is working on KIDA?
The current administrator of the database is Valentine Wakelam (Laboratoire d'Astrophysique de Bordeaux, France). Pierre Gratier (Laboratoire d'Astrophysique de Bordeaux, France works on the content of the database while Benjamin Pavone (Laboratoire d'Astrophysique de Bordeaux, France) is the web developer.
The experts in physics and chemistry who are working on the data present in KIDA are listed here.
If you have any comments or bug reports, please send an email to kida-obsu-bordeaux.fr.
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How can I submit data to KIDA?
You need to download templates in the csv format, fill out the file with your data and send it to us by email. For any addition of new channels or reactions, you need to add rate coefficients as well as a reference. Your data submitted to KIDA is sent to experts for validation.
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I have submitted data to KIDA but I would like to modify it, how can I do?
No you cannot. If you need to do it, contact the KIDA team directly.
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How can I notify KIDA that there is a mistake in some data?
You can send an email to kidaobs.u-bordeaux1.fr and we will take care of the problem.
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What are the quality indicators of the rate coefficients?
Quality indicators are of four types:
  • Not recommended value
  • Not rated value
  • Valid value
  • Recommended value
« Not recommended » means that either we have found a mistake in the data or there is a more accurate value to use. We do not erease any value from KIDA, this is why we use this indicator. « Not rated » means that we do not know. « Valid » is used for data with a proper reference (usually papers published by physico-chemists). « Recommended » is used for reactions that have been studied by KIDA experts and a datasheet explaining the recommendation is also available.
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What are the methods mentioned for the data?
For most of the data (rate coefficient, desorption energies etc), the method is given. It can be:
  • Measurement : this means that the data has been obtained experimentally.
  • Theoretical : this means that the data has been theoretically computed.
  • Review and evaluation : this means that the value is the result of a compilation of published data.
  • Estimation : this means that it is a guess. This can be an educated guess though.
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What are the different possible origins for the data?
The different origins can be:
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Can I add species not present in KIDA yet?
Yes you can but you will be asked for all the information that has to appear in KIDA.
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Are data erased from KIDA?
No, once a data has been accepted in KIDA, we never erase it. If a data appears to be wrong, we use the quality indicator.
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Can several rate coefficients appear for the same channel?
If several data exist (from different groups for instance) for the same channel for the same or different ranges of temperature, they will all appear on the reaction page. On the seach result page, only the « best » value will appear.
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Where can I find the references for data stored in KIDA?
You can find them here.
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How should I reference to the database?
The answer is here.
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How are rate coefficient uncertainties defined in KIDA?
See the answer here.
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What are the kida.uva.xxx chemical networks?
kida.uva.xxx networks are a selection of gas-phase chemical reactions extracted from KIDA that can be directly used in astrochemical models for the interstellar medium. These networks are regularly updated. The current versions are:
  • kida.uva.2011 (Wakelam et al. The Astrophysical Journal Supplement, Volume 199, Issue 1, article id. 21, 10 pp. (2012))
  • kida.uva.2014 (Wakelam et al. The Astrophysical Journal Supplement Series, Volume 217, Issue 2, article id. 20, 7 pp. (2015))
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What are the units used in KIDA?
Masses: amu
Temperature: K
Dipole Moment: Debye
Rate coefficients for photo and cosmic-ray processes: s-1
Rate coefficients for bimolecular reactions: cm3s-1
Rate coefficients for termolecular reactions: cm6s-1
Polarizability: Å3
Enthalpy of formation and reaction: kJ mol-1
Desorption energy: Kelvin
Diffusion energy: Kelvin
activation energy: Kelvin
Barrier Width (for surface reactions): Angstrom
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What are the types of reactions?
In KIDA, there are four big famillies of reactions:
  • Unimolecular reactions include dissociations and ionizations by cosmic-ray particules, secondary UV photons induced by cosmic-ray particles and direct UV photons. ITYPES 1 to 3.
  • Bimolecular reactions includes all chemical reactions between two species. ITYPES 4 to 8
  • Termolecular reactions are 3-body asssisted reactions.
  • Surface reactions are reactions occuring at the surface of interstellar grains between adsorbed species.
ITYPE Description
1 Dissociation or ionization of species due to direct collision with cosmic-ray particles.
2 Dissociation or ionization of species due to UV photons emitted following H2 excitation.
3 Dissociation or ionization of neutral species by UV photons with a standard interstellar UV field.
4 Neutral-neutral (A + B → C + D), ion-neutral (A+ + B → C+ +D, A- + B → C- + D), anion-cation (A+ + B- → C + D) reactions and associative ionization (A + B → AB+ + e-)
5 Exchange reaction A+ + B → A + B+ and A+ + B- → A + B
6 Association reactions between two species (neutral or ionized) stabilized by the emission of a photon (A + B → AB + photon or A+ + B → AB+ + photon).
7 Association of a neutral species and an anion, resulting in the ejection of the extra electron (A- + B → AB + e-).
8 Recombination of a positive ion with an electron resulting in the dissociation of the molecule (AB+ + e- → A + B) or the emission of a photon (AB+ + e- → AB + photon) or the attachment of the electron (A + e- → A- + photon)
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Which formula are used to compute the rate coefficients (for gas-phase reactions) from the parameters stored in the database?
Five different formula can be used to compute the rate coefficients from the parameters listed in KIDA.
Number (for export) Name Formula Units
1 Cosmic-ray ionization troe s-1
2 Photo-dissociation (Draine) troe s-1
3 Modified Arrhenius troe cm3 s-1
4 ionpol1 troe cm3 s-1
5 ionpol2 troe cm3 s-1
6 3-body See here
For information on the ionpol1 and ionpol2 formula see here.
For information on the visual extinction Av see here.
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What are the photorates in KIDA?
The rate coefficients given in KIDA have been calculated for the standard interstellar radiation field cf. Draine (1978, ApJS, 36, 595). See also here.
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Where do the formula for unmeasured ion-polar reactions come from?
Some explanations on the computation of the rate coefficients for unmeasured ion-polar reactions, i.e. using the ionpol1 and ionpol2 formula can be found here.
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Explanations on 3-body reactions
The pressure dependency of the rate coefficient is expressed as:
formula

The broadening factor F is the factor by which the rate constant of a given recombination reaction at temperature T and at the reduced pressure Pr is reduced from the value it would have if recombination reactions behaved according to the Lindemann formula.
The reduced pressure Pr is compted by Pr =k0[M]/kinf with [M] the concentration of the third body.
k0 and k∞ are function of temperature computed with the Kooij formula. k0 is the low-pressure limiting form whereas kinf is the high-pressure limit. Both rate constants have the following unit: cm6.molecules-2.s-1.

The broadening factor F for every reduced pressures Pr is computed as:
formula
c = - 0.4 - 0.67 x log10(Fc)
N = 0.75 - 1.27 x log10(Fc)
d = 0.14

In some cases, Fc can be calculated as a function of temperature from the Troe's fall-off parameters a, b, c, and d by:
formula
a is dimensionless and b, c and d are in K (T as well of course).

When no specific Troe fall-off parameters can be retrieved from the literature, it can be assumed Fc = 0.64, following the simpler policy chosen by the NASA/JPL evaluation panel (Sander et al., 2006).
In KIDA, you will find Fc and the parameters to compute k0 and kinf.

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Explanations on surface reactions
To reproduce the surface chemistry on interstellar grains, we provide chemical reactions (i.e. reactants and products) with branching ratios, activation energies (when appropriate). For reactions with activation energies, the barrier can be overcome by tunneling, in that case, the width of the barrier is given. Explanations on who to treate the tunneling in chemical model scan be found here (TODO). Concerning parameters for the surface reactions and gas-grain interactions, the available data is very sparse. So as a start, we have put in the database what we have been using in our models. A BIG work on quality data have just started.
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How to define the surface types?
We classify the surface types into hierarchical categories (see classification below). Data providers can nevertheless provide data for other surfaces by describing the method necessary to reproduce these surfaces.
troe
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Links and documents about chemical processes
  • Photo-processes: Many information about the computation of the rates of photo-reactions can be found in Ewine van Dishoeck's web page at the University of Leiden (Netherlands): here.
  • The ISSI Team: To improve our knowledge on the kinetic of cold interstellar regions, we made a group of both astrophysicists and physico-chemists. Two meeting of this group in Bern (Switzerland) were funded in 2008 by the International Space Science Institute (http://www.issibern.ch/). The results of our discussions have been written in an article submitted to Space Science Reviews and can be downloaded here.
  • The UMIST Database for Astrochemistry (http://udfa.ajmarkwick.net/)
  • The NIST webbook (http://webbook.nist.gov/chemistry/form-ser.html)
  • The OSU databases (http://faculty.virginia.edu/ericherb/research.html)