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Energy Level Plot Window

This window can be used to display a wide variety of energy level plots. The plot below is a typical linear molecule plot, showing the rotational levels of the ground X 3Σ -state of SO. Plotted as a function of J, in shows the F1 F2 and F3 components as a function of J. Note that BJ(J+1) has been subtracted from the vertical scale, so that the deviations from the simple BJ(J+1) pattern are clear. The actions of the various controls are listed below.

ActiveObject Select which states to plot.
ListButton Write the plotted energy levels to the Log window
AnotherButton Open another level Window

Plot Type

PlotTypeGroup The options in this group control the overall appearance of the plot.
ExternalField Plot against external field, rather than quantum number. See Electric or Magnetic Field Plots for more details.

Select to plot absolute symmetry, rather than J adjusted symmetry.
CalcPoints Plot a symbol for each level. The key to the symbols will normally be shown at the top of the plot, and different symbols indicate different symmetries.
CalcLine Join associated levels with lines. The levels joined are controlled by the three options below.
CalcBoth Plot both points and lines.
JoinHighest Choose between starting join process from the highest energy or lowest energy point
TrackQuanta Try to join points with related values of quantum numbers
TrackState Try to join points arising from same state

Energy Scale

EScaleGroup The options in this group control the vertical scale of the plot
Label2Ymax Maximum energy in plot
Label3Ymin Minimum energy in plot
RefreshPlot Refresh Plot (only needed if AutoReplot turned off in mixture)
AllButton Adjust plot range to include all levels
ZoomButton Zoom to selected vertical range
ZoomOutButton Compress vertical scale
Label6ReductionLabel7 Subtract number × J(J+1) from all energies plotted

Level Selection

SelectGroup This group allows levels to be selected by symmetry or some other quantum numbers. The picture is for a linear molecule; alternate quantum numbers are selected for other molecule types.
Label10Symmetry Select (or not) symmetry to plot

Limit J range plotted to Jmax for manifold.
ALabelASelect Select Ω (linear molecules), Ka (asymmetric tops) |K| (symmetric tops) or v1 (Vibrating molecule).
BLabelBSelect Select Fn (linear molecules), Kc (asymmetric tops) or Kl (symmetric tops).

x Axis

QuantumNumberGroup For normal plots, this controls the x axis.
XQuantumLabelXQuantumNumber Select quantum number for x axis
Label4XMin Minimum J to include in plot
Label5XMax Maximum J to include in plot

Observed Level Overlay

It is possible to compare calculated and observed energy levels, with the "observed" energy levels calculated by combining the measured line positions with the calculated energy levels for the other state. This requires an experimental line list (a .lin file), made as described in line position fitting. To include experimental information:

  1. Make sure the line list file is set in the Log window.
  2. Select ObsUpper to plot upper state energy levels or ObsLowerButton to plot lower state energy levels.
  3. Press Reload
          Button to display the observed energy levels.
  4. The display is normally clearer if CalcLineButton is selected for the calculated energy levels.
  5. If the mouse is over an experimental point it's source is displayed in the status bar; right click offers the following options:
ObsUpper Plot Upper State Observed Levels: Eobs = Elower + νobs
ObsLower Plot Lower State Observed Levels: Eobs = Eupper - νobs
JoinObs Join observed point to calculated point
ReloadButton (Re)load observations
Label11ErrorMultiplier When plotting observed energy levels, scale the distance from the calculated position by this. If a negative value is given, then the plotted point is Ecalc + (Eobs-Ecalc)/σ, where σ is the estimated error of the observation. If Exclude Perturbations is set, then perturbations are excluded from calculating Ecalc, but not from the Elower or Eupper value used in calculating Eobs.

Calculation Adjustment

ExcludeGroup This group allows the selected items to be excluded from calculations
ExcludePerturbations Exclude perturbations in plotted levels
Label13IgnoreSpins Set how many nuclear and electron spins to exclude from the calculation

Line Labels

Where to place labels on calculated lines. Possible choices are:

  • None
  • LeftOut: At left edge of plot, right justified
  • LeftIn: At left edge of plot, left justified
  • RightIn: At right edge of plot, right justified
  • RightOut: At right edge of plot, left justified
  • Start: At start of the line
  • End: At the end of the line