Molecule Types Asymmetric Tops <Prev Next>

Asymmetric Top Molecule

These are the settings for an asymmetric molecule as a whole, i.e. those common to all states (but perhaps different for different isotopologues).


nNuclei Number of nuclei to calculate hyperfine structure for. Leave this at 0 unless you want the hyperfine structure resolved.
Jmin Minimum J to use in calculation - set to -1 (default) to use value from the species.
Jmax Maximum J to use in calculation - set to -1 (default) to use value from the species.
Colour Colour - set to "None" to take value from elsewhere as explained in Determining Colours and J ranges.
JAdjustSym If set, energy level plots and Fortrat diagrams will take account of the alternation in symmetry with J that is often found. For example the E+ and E- Wang matrices will alternate in J for selected point groups - see Axis systems and symmetries for asymmetric tops for more details.
BlockMatrix Set to force check of Hamiltonian matrix for factorization into blocks before diagonalization. If blocks are found, these are diagonalized separately, ensuring states that have no connecting matrix elements are not accidentally mixed if the eigenvalues happen to be very close. In principle, if full use is made of symmetry and states are separated into separate manifolds as appropriate, this should not be necessary but can easily happen if selected terms in the Hamiltonian are zero or interactions between states are omitted.
AbsoluteE True if energies have not been offset. This is not the default for compatibility with previous versions, though perhaps should be for new calculations. Setting this false (the default) allows transitions with negative frequencies, which can occasionally be convenient for simulations involving a small spread of frequencies around a large central frequency where a large offset is applied to the upper state origin. This can give erroneous negative frequencies; while there is logic to detect common cases where this might arise, some calculations (typically involving near degenerate manifolds) require this to be set to true for correct operation.
PointGroup Point group - C1, Ci, C2, Cs, D2, C2v, C2h or D2h
Representation Representation - Ir, IIr, IIIr, Il, IIl or IIIl
SReduction Use Watson's S reduction (as opposed to A).
eeWt Statistical weight for ee levels for totally symmetric vibronic states. The weights will be permuted appropriately for vibronic states of other symmetries. Note that any nucleus for which hyperfine structure is to be calculated should not be included in calculating the statistical weights - see under the nucleus settings for notes on the required calculation.
eoWt Statistical weight for eo levels for totally symmetric vibronic states.
oeWt Statistical weight for oe levels for totally symmetric vibronic states.
ooWt Statistical weight for oo levels for totally symmetric vibronic states.
C2zAxis a, b, or c; C2 axis in C2v, C2 or C2h; axis perpendicular to symmetry plane in Cs - see Axis systems and symmetries for asymmetric tops
C2xAxis a, b, or c; typically the out of plane axis in C2v, but either of the two axes that are not the C2 axis can be chosen, and both possibilities are common in the literature. See Axis systems and symmetries for asymmetric tops for more discussion.
PseudoC2v Ignore any operators breaking C2v symmetry - see Pseudo C2v Symmetry
FakeSym Turn off transition moment test - see the discussion in Pseudo C2v Symmetry
PhaseAdjust Multiply the basis states by a phase factor chosen to reduce the number of imaginary matrix elements. The factors are:

K even, +
K even, -
K odd, +
K odd, -
N even
N odd
See the description of the basis states used.
SingleSubBasis Set true to use a single sub-basis for a given state, rather than splitting E+/E-/O+/O- Wang symmetries. For lower symmetry molecules, where the Wang symmetries are mixed, this can produce different assignments of the Ka and Kc quantum numbers, and for a single state will force the standard asymmetric top energy order, provided BlockMatrix is false.


Abundance Abundance of this isotope; default is 1
AssumedOrigin Can normally be left at the default value; see the generic Molecule entry for more information