Interf Check

n*λ = 2d*sinϴ*(1-k/n²)

n is the order of diffraction,
λ is the wavelength of the X-ray line,
2d is the interplanar spacing of the diffracting crystal or multilayer device,
ϴ is the angle of diffraction,
k is the refraction factor of the diffracting crystal or multilayer device.

CAMECA spectrometers are geared in “sinϴ steps”, where 1 step is equal to a sinϴ difference of 0.00001, or 1*10^-5. Thus, a spectrometer position of 60000 is equal to a sinϴ value of 0.60000. The range of a standard spectrometer is from ~0.23 to ~0.84 sinϴ, while the extended range spectrometer has a range of ~0.23 to ~0.93 sinϴ

The values of 2d and k for each crystal or multilayer device are taken from the Configuration program, Crystal panel.

Selection of elements and filters

To select an element, click on the element in the periodic table to select the commonly used X-ray line for that element at the selected beam voltage. To choose another line (less commonly used or from another transition level), RMB click on the element to access a drop down menu and choose the desired line, then LMB again on the element to select the element and new line in the list.
The output may be filtered by beam accelerating voltage, maximum order and explored range. The HV (kV) field (beam voltage) is automatically read from the column, or may be entered manually, and sets a limit on the maximum X-ray excitation energy. X-ray lines with an excitation energy greater than the beam voltage will not be shown. Maximum Order limits the display to the first n orders of X-ray lines. The Explored Range sets the boundaries, in the number of spectrometer steps around the analytical X-ray line, within which potential interferences will be displayed.

Output

As elements are selected, results appear in a separate ‘Overlap’ window.
The following data is displayed: Atomic number (Z), Element name, X-ray name, X-ray order (n), n*Lambda (Å), X-ray energy (keV), Theoretical intensity (arbitrary units, dependent on HV), and Position of the X-ray line, in sinϴ units.
For each analytical X-ray line (Reference), the position shown is the absolute position of the X-ray line on the spectrometer for each crystal.
After each reference X-ray line, potential X-ray line Interferences are shown in relative positions from the reference line, in sinϴ units. For example, a value of 600 means that the interfering line is located 600 steps away from the reference line, at a higher sinϴ position. Negative values indicate that the interfering line is at a lower sinϴ position, relative to the reference line.
In the output window, it is possible to select/deselect display of crystals and elements by using the checkboxes on the left panels.

Options 

1. If the interfering line is from an element of very low concentration in the sample (or standard), there is less concern than if the interfering element is of high concentration.
2. Interfering lines of higher order (n > 1) will be much lower in intensity than first order lines (n = 1).
3. Interfering lines with n > 1 can be suppressed by proper use of PHA (Pulse Height Analysis) discrimination.  Lines with n = 1 cannot be suppressed with PHA.
4. Choosing a background offset position greater than that of an interference position does not necessarily include the interfering line in the background counts.  For example, if there is an interfering line at -600, choosing a background offset of -1000 does not mean that counts from the interfering line at -600 will be included in the background measurement at -1000.  WDS is not (usually) an integrating technique, but instead collects counts at discrete wavelength positions.
5. If there is a major overlap on an analytical peak, consider using another crystal (e.g., LiF instead of PET for V Ka) or another analytical line (e.g., V Kb instead of V Ka).
6. If a calibration standard contains an element that will not be included in the quantitative analysis of the unknown samples, it is not necessary to specify an analytical line for that element. However, it is still important to select the element itself, in case there is an X-ray overlap that could affect calibration on the standard.
7. How close is too close for an interfering line?  The answer will vary with the diffracting crystal, the concentration of the interfering line, and the expected concentration of the sample.  Anything with an offset of less than a few hundred steps should be carefully considered.
8. There is a peak overlap correction available in the Quantitative analysis software that can mathematically suppress interferences for all orders.
9. For trace element analysis, the Check Interference program is a good first step.  Further evaluation should be made with real spectra acquisition and quantitation on blank samples.

Nomenclature

Conversion of output display to Siegbahn notation.