Objects Mixture <Prev Next>

Simulation

There is one of these objects for each simulation. The first one is for the main window, with others for each plot window. The settings can all be adjusted from the Constants window, and some can also be adjusted from menus in the main window and text boxes in the main window and plot windows.

Settings

IntensityUnits Units for intensity. Possible values are:
  • Arbitrary - fastest, but can give misleading results (see below).
  • Normalized - include partition function
  • Squared - square the calculated intensity
  • HonlLondon - The line strength factors, essentially the transition dipole moment summed over all the degenerate M levels and squared.
  • EinsteinA - The Einstein A coefficient for each transition. This is summed over lower state M levels, but not upper state levels, so corresponds to the lifetime of the upper state. Population factors are also excluded.
  • nm2MHzperMolecule - for normal absorption
  • cm2WavenumberperMolecule - for normal absorption
  • HzperMolecule - for emission. This is the rate of emission of photons by one molecule on each transition, including the Boltzmann factor and partition function.
  • PopDist - for a time of flight spectrum or similar experiment where energy levels are observed directly, rather than transitions
  • NormPopDist - as for PopDist, but include partition function.
For the four with units (EinsteinA, nm2MHzperMolecule, nm2MHzperMolecule and HzperMolecule), transition moments are assumed to be in Debye.

Misleading results can be obtained for a setting of Arbitrary when simulating isotopologues or isotopomers with different symmetry or statistical weights together, such as 35Cl2 and 35Cl37Cl. The calculation is "correct", in that the partition function is necessary to give the correct relative intensities, but is excluded by design for this setting.
LifeModel Model to use for state dependent lifetimes and linewidths. Valid values are lmNone, lmWidth, lmProduct, lmProductWidth, lmParent, lmParentWidth, lmGate, lmGateWidth. See Widths and Lifetime Effects for how this setting works.
PlotUnits Units for the horizontal scale for spectrum plots. Possibilities are as for Units above (the calculation units) and also:
  • sqrtcm1 - Velocity in units of cm-1/2
  • nmVac - Wavelength in vacuum in nm
  • nmAir - Wavelength in air in nm
nDF Number of points (between Fmin and Fmax) to calculate the spectrum at. Note that if a peak width is less than 3*(Fmax-Fmin)/nDF, i.e. only a few points wide, then it is shown as a stick, rather than a peak.
WidthMult Multiple of line width to extend convolution over.
ShowSum Plot overall sum of individual spectra. This is toggled by the button.
ShowParts Plot individual spectra making up overall spectrum. The individual spectra are grouped by colour, so you will need to set colours to see something different to the sum. Colours can be set at the transition moment, state, molecule or species level. This is toggled by the button.
ShowFortrat Plot a Fortrat diagram, i.e. J against frequency, in the main window. This is toggled by the button.
UseUpper Set to use upper rather than lower state J and symmetry in the Fortrat diagram.
ShowSymmetry Show symmetry in Fortrat plots.
ShowDeltaJ Show change in J in Fortrat plots.
ScaleMarkSize Scale Mark Size with intensity in Fortrat plots.
UseSymmetry If true, show different symmetries in separate Fortrat plots.
UseStateNumber If true, show different state numbers in separate Fortrat plots.
FortratQno Select quantum number to use in Fortrat plots.

Parameters

Several of these can be set from the tool bar in the main window.
Fmin Left edge of plot range in main window.
Fmax Right edge of plot range in main window.
Temperature Rotational temperature (Kelvin).
Gaussian Gaussian contribution to linewidth (full width half maximum). If both this and a Lorentzian width (below) is set the result is a convolution of the two, a Voigt profile.
Lorentzian Lorentzian contribution to linewidth (full width half maximum). This and the Gaussian width can also be set from the main window.
Foffset Frequency offset to simulation.
SMargin Relative Size of peak to ignore when convoluting for contour fitting.
OThreshold Ignore peaks smaller than this fraction of the maximum peak intensity.
RefWidth Reference width in linewidth (predissociation) calculations; see LifeModel
Tvib Vibrational Temperature (Kelvin); set to -1 (default) to use rotational temperature for all Boltzmann factors.
MinI Set the scaling of mark sizes in Fortrat plots.
Saturation Zero for normal calculation; positive values progressively switch strength to population only by replacing the line strength, S by:
S = (1-exp(-S*Saturation/g))*g
where g = Min(2J'+1, 2J"+1)*Statistical Weight. This is appropriate for saturation by z polarized light. Values of, say, 1 to 10 will wash out the differences between allowed branches and much higher values will bring out transitions that are only allowed by some weak mixing.
EField Static electric field, V/m; see External Fields - The Zeeman and Stark Effects
BField Static magnetic field in Tesla (= 104 Gauss); see External Fields - The Zeeman and Stark Effects