Chemistry Reference
In-Depth Information
or emitted by substances reveals information on the nature of the
constituent atoms, while the intensity of the radiation absorbed or emitted
is indicative of the relative amounts of specific atoms in a substance.
Atomic absorption spectroscopy
is based on the detection of the specific
wavelengths of light depleted by atoms in a material from a continuous
source of energy.
Atomic emission spectroscopy
rests on the detection
of the characteristic wavelengths of the light emitted by atoms heated
to high temperature (Young and Pollard 2000; Metcalfe and Prichard
1987).
Mössbauer spectroscopy
is an analytical technique that, in archaeo-
logical ceramic studies, provides information on the condition and charac-
teristics of the compounds of iron in pottery. Using the technique makes
it possible to determine the relative amounts of the different (ferrous and
ferric) ions of iron and hence to ascertain the firing conditions of the
pottery at the time it was made. The technique involves irradiating a
sample of pottery with gamma rays and then assessing the amount of
radiation absorbed by the nuclei of the ions of iron within the pottery
(Feathers et al. 1998; Béarat and Pradell 1997).
Nuclear magnetic resonance spectroscopy is a technique that, based
on the magnetic properties of nuclei, reveals information on the position
of specific atoms within molecules. Other spectroscopic methods are based
on the detection of fluorescence and phosphorescence (forms of light emis-
sion due to the selective excitation of atoms by previously absorbed elec-
tromagnetic radiation, rather than to the temperature of the emitter) to
unveil information about the nature and the relative amount specific
atoms in matter.
X-rays Technology
Analytical
X-rays
techniques are used to characterize solids in a number of
ways. X-rays penetrate solids opaque (impenetrable) to visible light but are
slightly attenuated by matter. Irradiating a solid object with
X-rays
in
radi-
ographic
equipment yields, therefore, an image, known as a
radiograph
of the internal structure of the object (Lang and Middleton 1997). Other
X-rays-based analytical techniques frequently used in archaeological
research include
X-rays fluorescence
and
X-rays diffraction
instruments.
X-rays fluorescence
(XRF) identifies the elemental constituents of a solid
by the wavelength of electromagnetic radiation emitted by the atoms in
the substance when excited by X-rays, while
X-rays diffraction
reveals the
internal morphology as well as the atomic and molecular structure of sub-
stances (Jenkins 1999; Cullity 2001).
