Perturbations describe an
interaction between two states. To add a perturbation, right-click
on the manifold in which the perturbation is required, and select
"Add new..."). The state(s) involved must also be specified; right
click on the perturbation and select Rename to bring up a dialog box to select the
states involved. There can be several perturbations acting between
any pair of states if required. It can also be useful to have a
perturbation acting within a particular state, as this can be used
to add terms to the Hamiltonian that are not part of the standard
Hamiltonian for the molecule, such as higher powers of J in centrifugal distortion.
These settings are common to all perturbations; more specific
settings are included in the sections for linear, symmetric, asymmetric and vibrating molecules.
||Index, starting from 1, of nuclear spin involved in
perturbation; 0 (default) for normal case where the
perturbation does not involve a nuclear spin.
||Scale factor with respect to preceding perturbation
||Size of perturbation.