37th annual conference of the European Group for Atomic Spectroscopy
http://www.egas37.org
[03 Aug 2005 - 06 Aug 2005]
Dublin City University, Dublin 9, Ireland
The 37th annual conference of the European Group for Atomic
Spectroscopy (Systems) section of the European Physical Society will encompass
the broad theme of atomic spectroscopy and its applications in ultrafast
science, BEC, anti-atoms, quantum ICT, precision measurement, photoionization,
plasma physics, etc. Abstracts from all branches of experimental and
theoretical atomic, molecular, and trans-condensed matter physics, as well from
interdisciplinary areas where the theme has significant impact such as
medicine, materials, analytical science, etc. are welcome.
Organiser: John T
Costello
Contact details
Dr. Peter van der Burgt
Secretary - Organising Committee
Dept. of Experimental Physics
NUI- Maynooth
Maynooth
County Kildare
Ireland
E-mail: egas37@may.ie
Tel: 00-353-1-7083782
Fax: 00-353-1-7083313
Atomic spectroscopy
Atomic spectroscopy is the determination of elemental
composition by its electromagnetic or mass spectrum. Atomic spectroscopy is
closely related to other forms of (The use of spectroscopes to analyze spectra)
spectroscopy. It can be divided by atomization source or by the type of
spectrocopy used. In the latter case, the main division is between optical and
mass spectrometry. Mass spectrometry generally gives significantly better
analytical performance, but is also significantly more complex. This complexity
translates into higher purchase costs, higher operational costs, more operator
training, and a greater number of components that can potentially fail. Because
optical spectroscopy is generally less expensive and has performance adequate
for many tasks, it is far more common. Atomic absorption spectrometers are one
of the most commonly sold and used analytical instruments.
Optical Spectrometry
Electrons exist in energy levels within an atom. These levels have well defined
energies and electrons moving between them must absorb or emit an energy equal
to the difference between them. In optical spectroscopy, the energy absorbed to
move an electron to a more energetic level and/or the energy emitted as the
electron moves to a less energetic energy level is in the form of a (A quantum
of electromagnetic radiation; an elementary particle that is its own
antiparticle) photon (a particle of light). Because this energy is
well-defined, an atoms identity (i.e. what element it is) can be identified by
the energy of this transition. The wavelength of light can be related to its
energy. It is usually easier to measure the wavelength of light than to
directly measure its wavelength.
Optical spectroscopy can be further divided into absorption,
emission, and fluorescence.
In atomic absorption spectroscopy, light is passed through a
collection of atoms. If the wavelength of the light has energy corresponding to
the energy difference between two energy levels in the atoms, a portion of the
light will be absorbed. The relationship between the concentration of atoms,
the distance the light travels through the collection of atoms, and the portion
of the light absorbed is given by the (Click link for more info and facts about
Beer-Lambert law) Beer-Lambert law.
The energy stored in the atoms can be released in a variety of
ways. When it is released as light, this is known as fluorescence. Atomic
fluorescence spectroscopy measures this emitted light. Fluorescence is
generally measured at a 90° angle from the excitation source to minimize
collection of scattered light from the excitation source. The wavelength once
again tells you the identity of the atoms. For low absorbances (and therefore
low concentrations) the intensity of the fluoresced light is directly
proportional to the concentration of atoms. Atomic fluorescence is generally
more sensitive (i.e. it can detect lower concentrations) than atomic
absorption.
Strictly speaking, any measurement of the emitted light is
emission spectroscopy, but atomic emission spectroscopy usually does not
include fluorescence and rather refers to emission after excitation by thermal
means. The intensity of the emitted light is directly proportional to the
concentration of atoms.
Mass spectrometry
Atomic mass spectrometry is similar to ther types of (Click link for more info
and facts about mass spectrometry) mass spectrometry in that it consists of an
ion source, a mass analyzer, and a detector. Atoms' identities are determined
by their mass-to-charge ratio (via the mass analyzer) and their concentrations
are determined by the number of ions detected. Although considerable research
has gone into customizing mass spectrometers for atomic ion sources, it is the
ion source that differs most from other forms of mass spectrometry. These ion
sources must also atomize samples, or an atomization step must take place
before ionization. Atomic ion sources are generally modifications of atomic
optical spectroscopy atom sources.
Ion and atom sources
Sources can be adapted in many ways, but the lists below gives a the general
uses of a number of sources. Of these, flames are the most common due to their
low cost and their simplicity. Although significantly less common,
inductively-coupled plasmas, especially when used with mass spectrometers, are
recognized for their outstanding analytical performance and their versatility.
For all atomic spectroscopy, a sample must be vaporized and
atomized. For atomic mass spectrometry, a sample must also be ionized.
Vaporization, atomization, and ionization are often, but not always,
accomplished with a single source. Alternatively, one source may be used to
vaporize a sample while another is used to atomize (and possibly ionize). An
example of this would be laser ablation inductively-coupled plasma atomic
emission spectrometry, where a laser is used to vaporize a solid sample and an
inductively-coupled plasma is used to atomize the vapor.
With the exception of flames and graphite furnaces, which are
most commonly used for atomic absorption spectroscopy, most sources are used
primarily for atomic emission spectroscopy.
Liquid-sampling sources include:
Flames (atom source)
Inductively-coupled plasma (atom and ion source)
Graphite furnace (atom source)
Microwave plasma (atom and ion source)
Direct-current plasma (atom and ion source)
Solid-sampling sources include
Lasers (atom and vapor source)
Glow discharge (atom and ion source)
Arc (atom and ion source)
Spark (atom and ion source)
Graphite furnace (atom and vapor source)
Gas-sampling sources include
Flame (atom source)
Inductively-coupled plasma (atom and ion source)
Microwave plasma (atom and ion source)
Direct-current plasma (atom and ion source)
Glow discharge (atom and ion source)
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