You may have up to three isotope configurations - (the abbreviation "isoconfig" may be used where required by space restrictions). To set up for isotope calculations, you must enter data in two or three places, the Isotopes dialog, the Observed Wavenumbers dialog and the Read Observed Spectra Data.
Isotopes dialog. This is accessed either from the Control window (Isotopes... button), or from the Input/Atom Types dialog. Spectrum 1 uses the atomic weights listed in the Atom Types dialog. For spectra 2 and 3, you specify the type numbers of all atoms whose atomic weights are to be changed. For example if S atoms with type 16 are to have atomic weight 36 instead of 32, you would enter 16 and 36.0. If more than one atomic type is substituted, for example types 16 and 116 for sulfur, both must be given. If the Calculate box is not checked, the 2nd and 3rd spectra will be skipped.
Observed Wavenumbers dialog. Here you select the configuration with the Isotope Configuration spin control.
Reading NRVS intensity data. This is done in the same way as for the base configuration, through the Read Observed Spectra Data, which is accessed through the Settings menu or the Parameters dialog from the Spectra window. The Read Observed ... dialog now has a Spectrum number option in the upper left.
The Spectra Window now also has the configuration ("isoconfig") option in the upper left. If you have read in observed data but have not entered a new isotope substitution configuration in the Isotopes dialog, you will have to recalculate. The PED will be for the selected spectrum.
Text Output. The listed data for individual modes, including atomic motions, energies, etc. is for the main or original isotope configuration. There are lists of modes for the main configuration and each of the isotope configurations. The modes in each species in the lists for isotope configuration are given in order of decreasing frequency, but this order may be different from that of the main configuration if the isotope shifts are larger than the intervals between modes - in other words modes strongly affected by the changed atomic weight may jump over others. There is a column labeled "Main" which gives the mode number in the main list to which the given mode corrresponds, and for which the isotope shift is computed.
Atoms Window. This will show the motions for the main (number 1) configuration.
Least Squares. The configurations (1 to 3) which are included are controlled by the check boxes in the Isotopes dialog. Of course you must enter either some Observed Wavenumbers for (step-by-step) refinement on frequencies, or NRVS intensity data for NRVS refinement.