Multielemental Techniques II

Three X-ray Techniques:

X-ray fluorescence (XRF) is the emission of characteristic ‘secondary’ (or fluorescent) X-rays from a material that has been excited by bombarding with high-energy X-rays or gamma rays. 

Following removal of an inner electron by an energetic photon provided by a primary radiation source, an electron  from an outer shell drops into its place.

In falling, energy is released in the form of a photon (X-ray), the  energy of which is equal to the energy difference of the two orbitals involved

XRF

– Samples bombarded with X-rays

- Non-destructive 

– Sensitivity 0.1% (1000 ppm)

Particle Induced X-ray emission (PIXE) – A powerful, non-destructive elemental analytical technique used routinely in heritage science to answer questions of provenance, dating and authenticity.

SEM-EDX is a powerful tool for forensic scientists, since it can be used to:

1. Classify evidence material (when no reference material is available);

2. Discriminate evidence material (when reference material is available); and

3. Simultaneously examine the morphology and the elemental composition of objects.

EDX

– Electrons bombard the sample  – Can be non destructive

SEM uses a beam of electrons to produce magnified images

Secondary Electrons (SE)

Back-scattered electrons (BSE)

X-ray techniques

– SEM-EDX

Three X-ray Techniques:

X-ray fluorescence (XRF) is the emission of characteristic ‘secondary’ (or fluorescent) X-rays from a material that has been excited by bombarding with high-energy X-rays or gamma rays. 

Following removal of an inner electron by an energetic photon provided by a primary radiation source, an electron  from an outer shell drops into its place.

In falling, energy is released in the form of a photon (X-ray), the  energy of which is equal to the energy difference of the two orbitals involved

XRF

– Samples bombarded with X-rays

- Non-destructive 

– Sensitivity 0.1% (1000 ppm)

Particle Induced X-ray emission (PIXE) – A powerful, non-destructive elemental analytical technique used routinely in heritage science to answer questions of provenance, dating and authenticity

SEM-EDX is a powerful tool for forensic scientists, since it can be used to:

1. Classify evidence material (when no reference material is available);

2. Discriminate evidence material (when reference material is available); and

3. Simultaneously examine the morphology and the elemental composition of objects.

EDX

– Electrons bombard the sample  – Can be non destructive

SEM uses a beam of electrons to produce

magnified images

Secondary Electrons (SE)

Back-scattered electrons (BSE)

X-ray techniques

– SEM-EDX