The profile graph shows the cross-section of your sample from the top at 0 down to the substrate.
Scattering length density is displayed as the line qcsq. Absorption is displayed as mu. For reflpol, the magnetic scattering length density is displayed as mqcsq and the direction as theta. Clicking any of these entries in the legend will toggle the line on the graph.
You can add and delete layers from the layer menu. Layer parameters can be entered in the layer table, or you can graphically manipulate the profile by clicking and dragging on the layer interfaces (dashed lines) and control points (colored squares). Press Escape to restore the parameter to its original value. Press the arrow keys to move by a single pixel, or Control+Arrow to move by 1/5 of a pixel.
Dragging the control points up and down changes the value for the layer, right and left controls the roughness for the layer. Press Shift while dragging to change both simultaneously.
The roughness algorithm is fraught with problems. Consult the roughness supplement for the nitty-gritty details. Quick summary: make sure D's are twice as big as R's. Also, avoid the tanh model: for small roughness, RO is the half-width at one-third maximum; for large roughness, RO is the full-width at one-third maximum.
Pressing Shift while dragging a layer interface will move the interface between two layers rather than changing the depth of one layer. Pressing Shift+Arrow will move the layer interface one pixel at a time. Note that reflpol has two sets of interfaces: one for magnetic layers and one for physical layers, labelled M# and N# respectively.
The resolution convolution is performed using only the q points found in the data files. Extremely thick layers will produce rapidly oscillating reflectivity which will not be convolved correctly. The actual limit is specific to the geometry of the experiment and sample. Rough guidelines for maximum film thickness are 500 nm for x-rays and 200 nm for neutrons.
The print button on the bottom of the page sends the profile graph to the printer. Shift-right-click on the reflectivity graph to print that.
The rescale button changes the axes so that the entire profile is displayed along with some room to resize the profile.