Cut trajectories

Use a cut with calculated momentum coordinates to show its trajectory on a converted constant energy surface. Start with angle-resolved data that has the required experimental configuration, work function, and normal-emission position.

Python

Select the cut in angle space. Calculate its momentum coordinates without interpolating its intensity. Convert the complete dataset for the constant energy surface:

binding_energy = -0.3

cut = data.qsel(beta=-10)
cut_with_momentum = cut.kspace.convert_coords()
converted = data.kspace.convert()

cut_path = cut_with_momentum.qsel(eV=binding_energy)
constant_energy_map = converted.qsel(eV=binding_energy)

Plot the calculated kx and ky coordinates over the converted intensity:

import matplotlib.pyplot as plt

import erlab.plotting as eplt

fig, ax = plt.subplots(figsize=(3.4, 3.0), layout="compressed")
eplt.plot_array(
    constant_energy_map,
    ax=ax,
    cmap="Greys",
    gamma=0.5,
    aspect="equal",
)
ax.plot(cut_path.kx, cut_path.ky, color="tab:red")

(Source code)

Angular cut trajectory overlaid on a converted constant energy surface

The line must remain inside the measured momentum coverage. A mismatch usually means that the cut and surface use different momentum-conversion parameters. See Converting coordinates only for the difference between calculating coordinates and interpolating intensity.

Figure Composer

Start with the same angle-resolved data used in the Python procedure:

  1. Open data in ImageTool Manager.

  2. Choose Edit ‣ Select Data…. Select beta=-10 with qsel, and set Result Placement to Open Child Window.

  3. In the original ImageTool, choose Edit ‣ Convert to kspace…. Configure the conversion and open the result as a child window.

  4. Convert the angular-cut child. Re-enter the same configuration, work function, normal-emission offsets, bounds, and resolution. Open the result as another child window.

  5. Add the converted volume and converted cut in Sources. Give them the aliases converted and converted_cut.

  6. Select each source in Sources. Enable the eV selection row, select qsel, and enter the same binding energy for both sources.

  7. Use one axes in Layout.

  8. Add an Image Plot step for converted. Set Aspect to equal.

  9. Add an Axes Method step after the image. Select plot and target the same axes.

  10. Set Plot data to Pick from data. For X, select converted_cut and kx. For Y, select converted_cut and ky.

  11. Set the line color and style as required.

ImageTool interpolates the angular cut during momentum conversion. The Python procedure uses convert_coords because only the trajectory coordinates are required.