|
X-ray Fluorescence Spectroscopy (XRF) is one of the most widely
used techniques for nondestructive analysis of bulk samples. XRF
can be used to rapidly identify most elements with an atomic number
equal to or greater than aluminum. Samples may be analyzed as powders
or solids without preparation. The XRF unit is mounted on a movable
chassis that allows the instrument to examine objects in situ.
In XRF, the sample is placed in a beam of high-energy photons produced
by an X-ray tube. Some of the inner-shell electrons of the sample's
constituent elements absorb enough energy to be ejected from the
atom. Outer-shell electrons fill the vacancies left and emit excess
energies as fluorescent x-rays. The characteristic peaks identify
the elements and the height of the peaks can determine the quantity
of each material present. XRF cannot be used to analyze hydrogen,
helium, and beryllium and detection limits for other light elements
are poor.
Applications:
Many different works of art are usefully examined, including paintings,
bronzes, sculptures, and polychromed surfaces. For example, analysis
of several bronzes by Renaissance sculptor Adriaen De Vries revealed
that the bronzes, while made all over Europe, were composed of the
same alloy, leading conservators to conclude that the artist was
a technical master as well.
XRF can identify:
- pigments in areas of a painting without removing a sample;
- major and minor constituents in bronze works of art;
- elemental composition in early photographs, costumes, and prints.
Further reading:
Scott, David A. "The application of scanning x-ray fluorescence
microanalysis in the examination of cultural materials,"
Archaeometry 44 (2002). In press.
|
 |
|
