Objects Mixture | <Prev Next> |

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.

IntensityUnits | Units for intensity. These are described in detail under Intensity Formulae.
Possible values are:- Arbitrary
- fastest, as it does not include the partition
function, but can give misleading results (see below).
- Normalized
- default, and recommended for most cases unless
absolute intensities are required.
- Squared - square the calculated intensity
- HonlLondon
- The line strength factors, essentially the transition
dipole moment summed over all the degenerate M levels
and squared. The value displayed is actually 3
*S*_{pol}, which is correct for one photon transitions, but see the discussion under Line Strengths for possible caveats for other types of transition. `OscillatorStrength`- The oscillator strength calculated from the line strength divided by the lower state degeneracy.
- EinsteinASum
- The Einstein A
coefficient for each transition summed over upper and
lower state M levels, with population factors excluded.
This was EinsteinASum
up to version 6.0.228.
- EinsteinA
- The Einstein A
coefficient for each transition summed over lower state
M levels, with population factors excluded. This
corresponds to the radiative rate from the upper state.
- 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 -
Plots an energy diagram, rather than a spectrum, with
intensities just the level population. This is intended
for modeling 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.
OscillatorStrength, transition moments are assumed
to be in Debye for electric dipole transitions and Bohr or
nuclear magnetons for magnetic dipole transitions.Misleading results can be obtained for a setting of Arbitrary when simulating isotopologues or isotopomers with different symmetry or statistical weights together, such as ^{35}Cl_{2}
and ^{35}Cl^{37}Cl. 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 standard energy units (cm1, MHz,
Kelvin and eV) as in the Mixture object and also:- sqrtcm1 -
Velocity in units of cm
^{-1/2} - nmVac - Wavelength in vacuum in nm
- nmAir - Wavelength in air in nm
- angVac - Wavelength in vacuum in Å
- angAir - Wavelength in air in Å
2, 71 (1966). |

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. |

AutoMin | If set, Ymin is
automatically updated to minimum point in plot range |

AutoMax | If set, Ymax is automatically updated to maximum point in plot range |

Fmin | Left edge of plot range in main window. |

Fmax | Right edge of plot range in main window. |

Ymin |
Lower end of current plot
range; overwritten with lowest value in current range if AutoMin set |

Ymax | Upper end of current plot range; overwritten with lowest value in current range if AutoMin set |

Temperature | Rotational temperature (Kelvin). Setting this < 0 will force the use of numerical populations for all manifolds, as described in Non-Boltzmann Populations. |

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 | This setting controls the number of extra points to
calculate at each end of the spectrum. (These points are not
plotted, but may be required to avoid artefacts in the
convoluted spectrum): If > 0: Number of extra points to calculate at each end If < 0: Number of points is | SMargin|*WidthMult*(Gaussian+Lorentzian) |

OThreshold | Ignore peaks smaller than this fraction of the maximum
peak intensity in selected simulations. In line listings,
lines with an intensity less than this are excluded from the
printout; in this case the value is absolute, rather than a
fraction of the strongest. Note that line lists produced by
File, Export, Line List use a separate value that is a
fraction of the maximum 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 | Discard lines weaker then this fraction of the strongest
in Fortrat plots. Note that the default for this increased
from 0 to 0.01 in 10.0.31. |

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. |

Tspin |
Spin temperature (Kelvin); set to -1 (default) to assume equilibrated nuclear spin states. If set >=0 then the fraction of molecules with each particular nuclear spin species (ortho/para for diatomics) is fixed at the fractions found at T = Tspin. This is often appropriate for molecular beams, where the nuclear spin states do not relax during the expansion. Note that the current implementation for asymmetric tops
fails if the statistical weight for two different spin
species is the same. |

EField | Static electric field, V/m;
see External Fields - The Zeeman
and Stark Effects |

BField | Static magnetic field in
Tesla (= 10^{4} Gauss); see External
Fields - The Zeeman and Stark Effects |

Doppler |
Plot each transition as two peaks, split by 2*Doppler*Centre Frequency. This gives the double peak structure often seen in Fourier transform microwave spectroscopy. |

PlotSplit |
Fraction of plot area to use for the
simulation where simulation and overlay plots are separated.
The possible range is -1..1, with 0.5 the default. Negative
values put the simulation, rather than the overlay, at the
top. |

Right click on the item in the constants
window for the following operations in addition to the
standard ones: