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Notes on common error messages

No error message, but no simulated spectrum either

No error message, but the simulated spectrum or exported plot does not look as expected

If the plotted spectrum shows with no net width to lines, either because you have not chosen to set one with "Gau" or "Lor", or because they are rather smaller than the effective plot resolution, then the resulting plot can easily be misleading. This is because of issues with closely spaced transitions - do they combine as one strong line or several weak ones? A physically meaningful plot is only guaranteed if the resolution of the plot, equal to (Fmax - Fmin)/nDF, is significantly less (by a factor of 3 or more) than the linewidth used for the simulation.

No error message, but the quantum numbers are not as expected

All quantum numbers shown, apart from total angular momentum and symmetry, can give strange computed values, particularly in the presence of state mixing, but also for certain combinations of parameter values and quantum numbers. The algorithm used by PGOPHER to determine quantum numbers is affected by the EigenSearch and LimitSearch settings in the Manifold. For linear molecules, see also the OmegaOrder setting.

Problem loading a .pgo or .ovr file

The PGOPHER native format .pgo and .ovr files must have the right extension to load correctly; when downloading from a web page or from an email the extension can sometimes be changed to .xml, or .xml is added to the filename. To fix this, simply rename the file to have the correct extension. (Versions of PGOPHER after 6.0.163 will load files that have been renamed in this way automatically.) If this is not the problem, both types of files are xml text files, and can be edited with most text editors.

"Overflow in Boltzmann"

Very low intensities

Only one or two lines plotted

Total intensity shown as Nan

Failure in partition function calculation - zero sum at J=15

All of these can result from a large negative energy causing the Boltzmann expression exp(-E/kT) to overflow, or to give an unphysical population for some high J levels. See the discussion of J range and Partition Functions for a discussion of the causes of this problem and possible solutions. Very low temperatures can also trigger this.

Progress dialog stuck on Partition Function sum

This can indicate too many levels included in the partition function, possibly because the parameters correspond to levels much too close together. See the discussion of J range and Partition Functions for a discussion of the causes of this problem and possible solutions.

"Odd and even numbers of electrons in xxxx"

Did you remember to set the right spin for all states? This results if, for example you have the changed the ground state to doublet and left the excited state as singlet (the default).

"Mix of integral and half integral quantum numbers"

The error message means that you have asked PGOPHER to calculate an impossible level, such as a J = 1/2 level for a triplet state. It typically arises because you have not set up the spin in all the states correctly.

"Singular Matrix"

When least squares fitting, this normally means that you have floated a parameter (or some combination of parameters) that is not determined from the supplied experimental data. For example, you may well see this if you attempt to float both the upper and lower state origin for a transition, as only the difference is determined. To fix this, float fewer (or at least different) parameters.

"Inconsistent Statistical Weights"

This error occurs when two states with the same J and symmetry but with different statistical weights are included in the same Hamiltonian matrix, or connected by a transition moment that does not involve spin.

No error message, but (unwanted) negative transition frequencies

This can arise if Initial is set false for a manifold. Setting Initial false is designed to handle spectra where the frequency scale is specified as an offset from an unknown centre frequency, but can give incorrect results in other circumstances.