Objects

To represent molecules and states making up the simulation, PGOPHER makes use of a hierarchy of objects. This works rather like a nested directory structure containing files except that each level can only contain certain types of object. These are no particular limits to the number of objects at each level, so that arbitrary combinations of spectra can be constructed, and multiple interacting (perturbing) states can be simulated. To view or edit any of these objects, use the tree view in the Constants window (View, Constants). The topmost object is a
Mixture which contains parameters such as linewidth and temperature which are common to all the molecules in the mixture. The name of the mixture is normally the filename. A mixture contains one or more:
Species which contain one or more isotopomers or:
Molecules These specify the settings such symmetry and statistical weight which are common to all the states within a molecule. There are three different types, depending on the type of molecule: LinearSymmetric Top and Asymmetric Top. Molecules contain two types of object
Manifolds provide a way of grouping states together, allowing perturbations to be simulated. Manifolds contain two types of object:
States which contain the band origin and rotational constants of a particular state. Again, these are specific to the type of molecule, with Linear, Symmetric Top and Asymmetric Top versions, depending on the Hamiltonian used. If nuclear hyperfine structure is to be simulated, then each state contains nNuclei:
Nucleus which contains the hyperfine parameters for each nucleus for the parent state.
Perturbation which describes an interaction or perturbation between two states. There is one of these for each perturbation parameter.
Transition Moments which describe the transitions between manifolds. One of these objects is required for each pair of manifolds that have transitions between them. They contain one or more individual Transition Moment objects, which can be of various types:
Cartesian, i.e. along a, b or c for Asymmetric Tops or:
Spherical which can be used for any molecule type, and are particularly appropriate for Raman and multiphoton transitions.
Spin for magnetic dipole transitions carried by the electron spin
Orbital for magnetic dipole transitions carried by the orbital angular momentum (Linear molecules only)

Overlays and Experimental Data

Experimental data used to overlay simulated spectra are also described by a similar, if simpler hierarchy of objects. These can be individually inspected using the tree view in the Overlays window (Overlays, Properties). The topmost object is:
Overlays, which can contain two types of object:
Experimental Plots, which contain the (frequency, intensity) points of an experimental spectrum and/or
Bitmap Plots, which contain an image for use where only a picture of the spectrum is available, but not the raw data.