|Objects Mixture Species Molecule||<Prev Next>|
To generate partition functions from an externally provided
table of values (such as those provided by HITRAN) add an
"InterpolatedPartitionFunction" object at the molecule level.
Provided the active property is set then, when requiring
partition functions, PGOPHER
will interpolate from the provided table, rather than attempting
a sum over all calculated levels. Unless several ground state
vibrational levels are included in the calculation, this
approach is likely to be necessary for full accuracy in absolute
intensities. To load the table, right click on the object in the
tree view and select "Import...";
a simple text file is expected with at least two values on each
line, the temperature (K) and the corresponding value of the
partition function (More columns can be present.) On loading the
file you will normally be prompted to select the columns
containing the temperature (T) and partition function
values, Q. After loading, the values will be visible as
extra parameters, and can be edited as with other values.
With this set up and active, the populations are taken as:
where Qext is the interpolated value derived from the values given. Emin is used if the AutoZero flag is on, and is the lowest calculates energy, and has the effect of shifting the energy origin of the calculated levels to zero. (The origin is otherwise dependent on how the data file is set up and the choice of the Hamiltonian.) Ezero is the origin used when the external partition function was calculated.
g/(Scale×Qext) exp( -(E-Emin-Ezero) / kBT )
|Active||If true, use this to generate the partition function|
|Order||Order of Lagrangian interpolation to use. The default is
4, as used by HITRAN
|AutoZero||If true, Emin in the
formula above is the lowest calculated energy. If false it
is taken as zero.
|Multiply||Partition function is taken as Q = Qcalc×
Qext rather than simply Qext.
If only one vibronic stae is included in the main
calculation, this is equivalent to providing the vibronic
Versions before 8.0.217 had Fractional instead of Multiply, and used Qcalc× Qext. Old data files are automatically converted on loading by taking the reciprocal of the values for Qext.
|Zero||Energy zero of the external partition function.
|Scale||Scale interpolated partition function by this|