The species involved in the CollisionDB processes are identified using the conventions of the pyvalem library:

  • Atoms are identified by their element symbols:
    • H
    • Li, etc.
  • Molecules are sequences of element symbols, possibly with their numerical stoichiometries given (no underscore characters, _):
    • BeH
    • H2O
    • CH3CH2OH
  • Any charges are specfied after the formula in the format +, -, +q, -q (no caret characters, ^):
    • H+
    • Be+4
    • CO3-2
  • Isotopes are specified in parentheses, with the mass number preceding the element symbol (no caret characters, ^); deuterium and tritium may be specified as D and T, respectively:
    • (6Li)
    • (13C)

Quantum states are specified in any order using the following conventions:

  • Atomic configurations as orbitals separated by a period, .:
    • 1s
    • 1s2
    • 1s2.2s
    • 1s2.2s2.2p4
  • Atomic term symbols as follows (2S+1)L_J: spin multiplicity, 2S+1, followed by orbital angular momentum quantum number label and, optionally, J quantum number; odd parity is optionally specified with the character (o):
    • 2P
    • 2Po_1/2
    • 4D
    • 1S_0
  • Individual quantum numbers as key-value pairs (no spaces around the = sign):
    • n=1
    • |m|=1
  • Linear molecule electron configurations:
    • 1σ2
    • 1σg2
    • 1sigmau2.2sigmag1
    • 1sigmag
    • 1σg2.1σu2.2σg2.2σu2.1πu4.3σg2
  • Molecular term symbols (with or without state labels):
    • 1Σ+g
    • 1SIGMA+g
    • a(3SIGMA-g)
    • X(3Π)
    • X(3PI)
    • A(1A")

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There are currently 122,568 datasets. Click for advice on specifying species and states.

Please contact ch.hill@iaea.org with any questions or comments about this prototype data service.

A description of three-letter process codes is given here.
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