Geology Reference
In-Depth Information
Short-wave infrared spectroscopy
One of several types of vibrational spectroscopy (see Raman
Spectroscopy) that employs the interaction of infrared (IR) radia-
tion and absorption in a sample. An IR source is either transmitted
or reflected off of a sample and a detector records the transmit-
tance or reflectance of the various wavelengths in the IR region of
the electromagnetic spectrum.
Stoichiometry
The quantitative assessment of atoms involved in the reactant and
products of a chemical reaction.
Thermal gravimetric analysis
An analytical technique based on the weight loss or gain of a sample
as a function of temperature.Weight lossmay be caused by the release
of gas from the sample during heating. Weight gain may be caused by
reaction of the sample with the atmosphere in the laboratory.
Unit cell
The smallest volume of atoms or molecules whose repetition at
regular intervals in three dimensions using symmetry operations
produces a crystal lattice.
Vacuum tube
A glass or ceramic tube that contains a high vacuum for the free
movement of electrons.
Voltage
The potential difference in joules per coulomb of electrical charge
between two points in an electrical circuit. When divided by the
resistance (ohms) between those points, the result is equal to the
current flowing between those points in amperes or coulombs per
second.
Wavelength dispersive spectrometers
Devices that detects a specific energy or wavelength of character-
istic radiations (e.g., Cu-K
α
1
) by geometrically positioning the
detector according to Bragg
s Law using a crystal with a known d-
spacing. This allow for improved detection limits when compared
to EDS.
'
X-ray fluorescence spectrometry
An analytical technique used to identify and measure the concen-
tration of elements in a sample by measuring the wavelengths of
radiation emitted from the sample when irradiated with X-rays.
X-ray goniometer
An motorized instrument used to orient a source of X-rays, a
sample, and a detector in X-ray powder diffraction studies.
X-ray powder diffraction
A special form of diffraction that detects all possible crystal
orientations by powdering the sample into many small, randomly
oriented particles. Moving the X-ray beam and detector through a
range of angles produces an X-ray powder diffraction pattern that
is unique to each crystal structure.
X-rays
High-energy electromagnetic radiation with wavelengths that
range from ~0.05 to 100 Å.
X-ray spectrum
A region of the electromagnetic spectrum that corresponds with
the energies needed to excite the core electrons in all the elements.
Each energy transition is recorded such that a sample
s elemental
composition can be determined by measuring the intensity and
position of peaks detected and recorded.
'
References
Bragg, W.L. 1912, The specular reflection of X-rays: Nature. 90, 410 p.
Calas, G., Hawthorne, F.C., 1988. Introduction to spectrographic methods. Rev. Mineral. Geochem. 18, 1
-
9.
