XRF Flashcards
As XRF is non destructive and portable it is Ideal for analysing….
Art and archeological artefacts.
Complements to….
Raman spectroscopy.
In EDS, the sample is irradiated with electrons, whereas in XRF the sample is irradiated with…..
A beam of X-rays
XRF is not useful for lighter elements, H, He, Li because….
They only have one shell, so don’t have electron transitions.
If an electron falls from a higher shell to a lower shell, the transition is referred to by the shell being filled.
If m1 falls to K it is a…..
K transition
A disadvantage of XRF over Raman is the beam is larger, meaning it….
Provides less detailed info about pigment distribution.
XRF can be fitted with a camera to allow….
The sample area to be well defined.
The energy of the peaks tells us….
Which elements are present.
The intensity of peaks can be compared with known standards to….
Find the quantity of element.
How are secondary X-rays formed?
Formed from a release of energy as an electron falls from a higher to lower shell.
The secondary X-rays result in….
Fluorescent radiation.
Each elements atoms have a characteristic fluorescence emission signal, used to….
Obtain info about major and trace elements within pigments.
The incident X-rays are….
Primary X-rays….
The secondary X-rays are….
Emitted Fluorescent X-rays.
XRF can be used for geological samples and results can be compared to….
Soil reference standards.
Three advantages of portable XRF systems…
Analyse many samples in a short time period.
Cost efficient method at field sites.
Over 100 samples can be analysed per day.
XRF is an example of WDS because….
Only a single grating is used for each element.
Using a single grating is a major disadvantage for determine unknown analytes. To overcome this 2 things can be done….
Multiple diffraction gratings can be used - simultaneous XRF Spec.
Diffraction grating can be moved to a different position relative to the sample and fluorescent X-rays, to allow f-X-rays of diff wavelengths to be separated and pass to the detector.
The distribution of peaks on the spectrum determines….
The presence of certain elements.
The intensity of each element is recorded and related to…
The amount of each element in the sample to determine composition.
Fluorescent X-rays are collimating into a beam, which passes through a….
Diffraction grating, which separates X-rays by their wavelength. X-rays of single wavelength pass to the detector.