Objects Mixture Species Molecule Manifold State | <Prev Next> |

Custom width functions provide an empirical way of specifying
quantum number dependent line widths and intensities; see Widths and Lifetime Effects for the overall
picture. These are created under the appropriate state object, and
allow the width to be specified in terms of selected quantum
numbers. A typical function might be:

kp*Sqrt(J*(J+1))

which would be appropriate for an inhomogeneous predissociation,
such as predissociation of a Σ state by a Π state. Use a negative width to indicate a state that should be excluded from the calculation, perhaps because it is above a dissociation limit.

Notes:

- The function is held in the comment field for the object; in the constants window an enlarged text window replaces the normal comments window.
- See expressions for more
details on format. (If you want to add comments to the function
use # or // to start the comment, or enclose it in {...} or /*
... */.)

- Any unknown variables in the function are automatically created as parameters on simulating, or on right clicking on the node and selecting "Check Variables"
- Unwanted variables that are no longer in the expression can be removed by right clicking on the parameter and selecting remove.

Result |
The width PGOPHER
would use if Active
is set to false |

E |
The state energy |

J |
J for the state |

Symmetry |
The symmetry number of the
state |

Index |
The eigenvalue number of the
state |

MJ |
M for the state - only set
if external fields are present_{J} |

Origin |
The origin of the vibronic state. This is
normally the value of the Origin parameter for the
state, but for linear molecules a correction is applied so
that the value is approximately the energy of the
lowest rotational level. (A similar offset is applied in the
vibrational structure mode.) |

EB |
The AssumedOrigin
for the molecule (if not set to the default) or else the
lowest vibronic state origin (defined as above), considering
only states for which Initial = True. |

Width | The calculated width for the state, before applying the custom width. This will be the same as the Result variable for this type of object. |

Additional quantum numbers are also available, depending on the molecule type. They are based on the dominant basis state, so may not be exact for strongly mixed states.

For asymmetric tops the standard quantum numbersFor linear molecules:

Omega |
The Omega quantum number |

Fn | The spin component, 1 for F_{1},
2 for F_{2}, etc.Note that for versions before 8.0.171 the values were divided by 2. |

For symmetric tops:

K |
The absolute value of K |

Kl |
The sign of Kl but separably
degenerate point groups have additional in this variable. |

For vibrating molecules:

v1, v2, ... |
Vibrational quantum numbers |

l1, l2, ... |
Vibrational angular momentum quantum number,
for degenerate modes only. |

Lambda |
Electronic orbital angular momentum, Λ. |

Omega |
Electronic angular momentum, Ω. |

In addition any parameter can be referred to by giving the name in dotted notation. For example the current value of

Active | Set true to use the function provided to calculate the
width |

nDebug |
If non zero, write the values of all the
variables and the value of the function on each evaluation
to the log window. See debugging
for options on the output. To see any output the expression
must not be blank - simply set to "Value" to see
the defaults in action. |