Visualize

The Visualize tab plots the results of the jobs: energy levels, level mixings, stick spectra, synthetic spectra and observed minus calculated residuals of the fits.

Start by choosing the type of file to display:

File type	Content	Produced by
jener.xy	Rovibrational energy levels as a function of J.	Level and spectrum jobs
jener.t (or starkl.t)	Same levels, with their full identification.	Level and spectrum jobs
Ener[_assign]_Pn	Energy levels and vibrational mixings as a function of J.	Level jobs with mixings
spectr.xy	Stick spectrum.	Spectrum jobs
spectr.t	Stick spectrum (detailed TDS format).	Spectrum jobs
simul.xy	Synthetic spectrum.	Simulation jobs
Pred_mix	Observed minus calculated positions or intensities.	XFit (and deprecated Fit) jobs

The formats of these files are described in the File Format section.

For the first types, a file dialog opens immediately in the home folder (see Toolbar), and the file is plotted as soon as it is selected. The Ener_Pn and Pred_mix files require a few more settings, described below.

Plot window

Stick spectrum (spectr.xy) of the ν₁/ν₃ stretching dyad of ¹⁸⁴OsO₄ (ν₃ region).

The name of the file is displayed at the top of the plot. The numbers in brackets in the middle of the axes give the spacing between two ticks. The position of the mouse, in the units of the data, is displayed below the plot.

• Zoom: drag the mouse with the left button pressed to draw a rectangle; the plot is zoomed on this rectangle when the button is released. The operation can be repeated.

• Unzoom goes back to the full plot.

• Print prints the plot, in landscape orientation.

• Reset All closes the plot and goes back to the choice of the file type.

Synthetic transmission spectrum (simul.xy) computed from the stick spectrum above.

Energy levels

The jener.xy and jener.t files contain the rovibrational energy levels of the upper polyad of a spectrum job, or of the polyad of a level job. Each level is drawn as a small horizontal line at its energy, as a function of J.

The energies are reduced: the rotational energy of the ground state, \(B_0 J(J+1) - D_0 J^2(J+1)^2\), is subtracted, so that the structure of the polyad is much easier to see. The jener.xy file already contains reduced energies, while the jener.t file (like the starkl.t file written by Stark calculations) contains the true energies: XTDS reduces them using the \(B_0\) and \(D_0\) values read in the header of the file.

Level mixings (Ener_Pn files)

The Ener_Pn and Ener_assign_Pn files, written by level jobs with mixings, contain for each level the decomposition of its eigenvector on the vibrational sublevels of the polyad. XTDS draws each level as a horizontal bar whose segments are colored according to the weight of groups of sublevels, called components. This shows at a glance how strongly the vibrational states are mixed.

Before plotting, fill the form:

• In the BASICS section, keep All Energ. and J selected to plot all the levels, or unselect it and give the energy (Emin, Emax, in cm^-1) and J (Jmin, Jmax) ranges to display. With an Ener_assign_Pn file, select Assigned to display only the levels involved in assigned transitions.

• Add File adds a file to the DATA FILES list. Up to 10 files, computed for the same polyad, can be plotted together.

• Add Component adds a component, i.e. a range of vibrational sublevels plotted with the same color. The sublevels are numbered as in the list displayed in the text area of the job creation forms (the same list is written at the beginning of the spectr.t and Pred_mix files). Components must follow each other: the lower limit of a component must be greater than the upper limit of the previous one. Up to 100 components can be defined.

• Save Comp. File saves the components in a component file, and Load Comp. File reads them back. This avoids defining the same components again each time the same polyad is plotted.

Click on Show to draw the plot. XTDS first proposes to save the components in a file.

Reduced energy levels of the Octad of ¹²CH₄. The eight components group the 24 vibrational sublevels of the polyad.

In the plot window, the list of the components is displayed on the left, in their colors. Click on a component to hide or show it.

Observed minus calculated (Pred_mix files)

The Pred_mix files, written by the fit jobs, contain for each assigned line the observed and calculated positions and intensities. XTDS plots the residuals (observed minus calculated), which is the best way to check the quality of a fit and to find the wrong assignments.

• Add File selects the file. For the files written by XFit jobs, which contain several transitions, choose the transition to plot in the Transition list.

• Plot versus selects the quantity used as X axis: the lower (Jinf) or upper (Jsup) J value, the Frequency or the Intensity of the line.

• Components can be defined as for the level mixings, using the vibrational sublevels of the upper polyad of the transition. Each residual is then colored according to the component containing the dominant vibrational sublevel of the upper level. Lines whose dominant sublevel belongs to no component are not plotted.

The residuals are plotted in frequency or in intensity depending on the file. Each point is drawn with a symbol depending on its mark in the assignment file:

• a cross for the lines with a + mark, taken into account in the fit;

• a square for the lines with a - mark, not taken into account;

• a rhombus for the lines with another mark, not taken into account either.

Frequency residuals of the ν₂/ν₄ Dyad of ¹²CH₄ as a function of the upper J value, after an XFit job.

In addition to the zoom, a right-click drag selects a region of the plot: a window lists the residuals it contains, with their mark, position, obs.-calc. value and assignment. This is the quickest way to identify an outlier, which can then be corrected in Spview.