- 4033 -
X-RAYS - to see atoms? Scientists have taken the world’s first
X-ray SIGNAL (or SIGNATURE) of just one atom. This groundbreaking achievement
was funded by the U.S. Department of Energy, Office of Basic Energy Sciences
and could revolutionize the way scientists detect the materials.
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---------------------------- 4033 - X-RAYS - to see atoms?
- Since its discovery by Roentgen in 1895,
X-rays have been used everywhere, from medical examinations to security
screenings in airports. Even Curiosity, NASA’s Mars rover, is equipped with an
X-ray device to examine the materials composition of the rocks in Mars.
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- An important usage of X-rays in science is
to identify the type of materials in a sample. Over the years, the quantity of
materials in a sample required for X-ray detection has been greatly reduced
thanks to the development of synchrotron X-rays sources and new instruments.
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- The smallest amount one can X-ray a sample
is in “attogram”, that is about 10,000 atoms or more. This is due to the X-ray
signal produced by an atom being extremely weak so that the conventional X-ray
detectors cannot be used to detect it.
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- Atoms can be routinely imaged with scanning
probe microscopes, but without
X-rays one cannot tell what they are made of. We can now detect exactly
the type of a particular atom, one atom-at-a-time, and can simultaneously measure its chemical state.
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- Once we are able to do that, we can trace
the materials down to ultimate limit of just one atom. This will have a great
impact on environmental and medical sciences and maybe even find a cure that
can have a huge impact for humankind. This discovery will transform the world.
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- An iron atom and a terbium atom were both
inserted in respective molecular hosts. To detect X-ray signal of one atom, the
research team supplemented conventional detectors in X-rays with a specialized
detector made of a sharp metal tip positioned at extreme proximity to the
sample to collect X-ray excited electrons.
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- A technique known as synchrotron X-ray
scanning tunneling microscopy or SX-STM. X-ray spectroscopy in SX-STM is
triggered by photoabsorption of core level electrons, which constitutes
elemental fingerprints and is effective in identifying the elemental type of
the materials directly.
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- When X-rays illuminate onto an iron atom,
core level electrons are excited. X-ray excited electrons are then tunnel to
the detector tip via overlapping atomic/molecular orbitals, which provide
elemental and chemical information of the iron atom. The spectrums are like fingerprints, each one
being unique and able to detect exactly what it is.
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- Using X-rays to detect and characterize
individual atoms could revolutionize research and give birth to new
technologies in areas such as quantum information and the detection of trace
elements in environmental and medical research.
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- By comparing the chemical states of an iron
atom and a terbium atom inside respective molecular hosts, we find that the
terbium atom, a rare-earth metal, is rather isolated and does not change its
chemical state while the iron atom strongly interacts with its surrounding.
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- Many rare-earth materials are used in
everyday devices, such as cell phones, computers and televisions and are
extremely important in creating and advancing technology. Through this
discovery, scientists can now identify not only the type of element but its
chemical state as well, which will allow them to better manipulate the atoms
inside different materials hosts to meet the ever-changing needs in various
fields.
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- They have also developed a new method
called “X-ray excited resonance tunneling or X-ERT” that allows them to detect
how orbitals of a single molecule orient on a material surface using
synchrotron X-rays.
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- This achievement connects synchrotron
X-rays with quantum tunneling process to detect X-ray signature of an
individual atom and opens many exciting research directions including the
research on quantum and spin (magnetic) properties of just one atom using
synchrotron X-rays.
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June
1, 2023 X-RAYS - to
see atoms? 4033
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--- Friday, June 2, 2023
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