Atom Trap Trace Analysis (ATTA) is an extremely sensitive trace analysis method developed by
Argonne National Lab
Argonne National Laboratory is a science and engineering research national laboratory operated by UChicago Argonne LLC for the United States Department of Energy. The facility is located in Lemont, Illinois, outside of Chicago, and is the larg ...
(ANL). ATTA is used on long-lived, stable
radioisotopes such as , , and . By using a
laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The fir ...
that is locked to an atomic transition, a
CCD or
PMT will detect the laser induced
fluorescence
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, tha ...
to allow highly selective, parts-per-trillion to parts-per-quadrillion concentration measurement with single
atom
Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons.
Every solid, liquid, gas, and ...
detection.
This method is useful for atomic transport processes, such as in the
atmosphere
An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A s ...
,
geological dating
Geochronology is the science of determining the age of rocks, fossils, and sediments using signatures inherent in the rocks themselves. Absolute geochronology can be accomplished through radioactive isotopes, whereas relative geochronology is pr ...
, as well as
noble gas purification.
ATTA measurements are possible only if the atoms are excited to a
metastable state
In chemistry and physics, metastability denotes an intermediate energetic state within a dynamical system other than the system's state of least energy.
A ball resting in a hollow on a slope is a simple example of metastability. If the ball i ...
prior to detection. The main difficulty to accomplishing this is the large energy gap (10-20 eV) between the
ground
Ground may refer to:
Geology
* Land, the surface of the Earth not covered by water
* Soil, a mixture of clay, sand and organic matter present on the surface of the Earth
Electricity
* Ground (electricity), the reference point in an electrical c ...
and
excited state
In quantum mechanics, an excited state of a system (such as an atom, molecule or nucleus) is any quantum state of the system that has a higher energy than the ground state (that is, more energy than the absolute minimum). Excitation refers to a ...
. The current solution is to use an
RF discharge, which is a brute force technique that is inefficient and leads to complications such contamination of the walls from ion sputtering and high gas density. A new scheme for generating a metastable beam which can achieve a cleaner, slower, and preferably more intense source would provide a substantial advance to ATTA technology. All-optical techniques have been considered, but have not yet been able to compete with the discharge source.
A new technique for generation of metastable
krypton
Krypton (from grc, κρυπτός, translit=kryptos 'the hidden one') is a chemical element with the symbol Kr and atomic number 36. It is a colorless, odorless, tasteless noble gas that occurs in trace amounts in the atmosphere and is often ...
involves the use of a two
photon
A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless, so they always ...
transition driven by a pulsed, far-UV laser to populate the excited state which decays to the metastable state with high probability.
References
Sources
*
*
Radiochemistry
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