Notes on common error messages

No error message, but no simulated spectrum either

A common cause of this is the transition moment between the states of interest; check that one is present, and that the component or axis is set to give a transition between the states involved.

"Overflow in Boltzmann for xxxxx: E=-nnnnnnn"

This results from a large negative energy causing the Boltzmann expression exp(-E/kT) to overflow. 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. This error message is likely to arise on upgrade to version 5.2, if you are using an observation file prepared for version 5.1. You may need to add the following directive to the start of the observations file:
QuantumNumberFormat 2J
See the upgrading section for more on this.

"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.