ARTEMIS - The path page
The path page is displayed whenever a Feff path is selected from the Data and Paths List. This page is used to establish the math expressions of the path parameters for this path.
At the top of the page is a line identifying which Feff calculation
this path is from. Below that are three toggles. One is used to
include of inlcude or exclude the path from use in the fit. There are
many other ways in Artemis to include and exclude paths other than
to use this toggle. See The Feff interpretation page
and artemis_menubar for more discussion of this. Also
Control-t is the same as clicking this toggle.
The second toggle is used to specify paths that you would like plotted after a fit (or sum of paths) is finished. By default, the data and the fit (or sum) is plotted after the fit (or sum) and no paths are plotted. Any paths selected for plotting will be added to the plot after the fit (or sum) is finished.
The third toggle is used to set which path is the default path for
evaluation of Def parameters after the fit. It is possible to write
math expressions which evaluate differently for different paths. An
example might be a math expression using the reff parameter. For
any such Def parameters, it is necessary to tell Artemis which path
should be used for the reporting of those parameters in the log file.
The default is to use the first path listed in the Data and Paths
List.
Below that is a box which summarizes the path. This gives some statistics about the path as well as displaying a color-coded ``map'' of the scattering path. The central atom is always displayed in red text. Other atoms are in black text. The grey text shows the length and scattering angle of each leg of the path. In the case of a high-order multiple scattering path which has legs which have a non-zero Eulerian eta angle between them, the eta angle will be displayed as well. If that last sentence was gibberish, it suffices to know that paths of that sort are almost never observable in real EXAFS data.
At the bottom of the page is the list of path parameters. This is the most important section of the page because it is here that the details of the fitting model are realized. There is an entry box for each of the various types of path parameters. The math expression approporiate for each parameter should be entered in the entry box.
When a Feff calculation is imported into Artemis, a set of automatic parameters are generated, entered into the list on the Guess, Def, Set page, and entered into the path parameetr boxes for each path imported. The default behavior of Artemis is to generate a set of parameters appropriate for a simple, single scattering, first shell fit. While it might be OK to immediately click the big green button, most fitting models will require substantial editing.
The right mouse button serves many important purposes on the path page. Clicking the right mouse button anywhere in one of the entry boxes will highlight the word underneath the cursor and post a menu. The entries in the menu are for for defining the word as a parameter on the Guess, Def, Set page. For each parameter type there is the option of jumping or staying. In either case, the parameter is defined and added to the list on the GDS page. For jumping, the GDS page is then displayed. For staying, the current path page remains displayed.
Right clicking on one of the path parameter labels will post a menu of functions related to defining path parameter math expressions. The ``Edit'' option will pop up a dialog used for entering a math expression and then optionally exporting its value to other paths. The ``Clear'' option doies just that.
The various ``Export'' options are ways of constraining path parameters to be the same for other paths. The ``Grab'' options make the current path parameter the same as the path parameter in the previous or following path.
The ``sigma^2'' label has some additional options. These insert the syntactically correct text appropriate to using either the Correlated Debye or single frequency Einstein models for the sigma^2 of the path.
To enable the display of spaces for the dphase, k_array,
amp_array, or phase_array path parameters, you must click on the
``Extended path parameters'' button in the Paths menu.