科学家拍摄到单个原子的影子照片

In an international scientific breakthrough, a Griffith University research team has been able to photograph the shadow of a single atom for the first time. "We have reached the extreme limit of microscopy（显微镜学） ; you can not see anything smaller than an atom using visible light," Professor Dave Kielpinski of Griffith University's Centre for Quantum Dynamics¹ in Brisbane, Australia.

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"We wanted to investigate how few atoms are required to cast a shadow and we proved it takes just one," Professor Kielpinski said.

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Published this week in Nature Communications, "Absorption imaging of a single atom "is the result of work over the last 5 years by the Kielpinski/Streed research team.

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At the heart of this Griffith University achievement is a super high-resolution microscope, which makes the shadow dark enough to see.

Holding an atom still long enough to take its photo, while remarkable² in itself, is not new technology; the atom is isolated³ within a chamber⁴ and held in free space by electrical forces.

Professor Kielpinski and his colleagues trapped single atomic ions of the element ytterbium and exposed them to a specific frequency of light. Under this light the atom's shadow was cast onto a detector⁵, and a digital camera was then able to capture the image. #

"By using the ultra hi-res microscope we were able to concentrate the image down to a smaller area than has been achieved before, creating a darker image which is easier to see," Professor Kielpinski said.

The precision involved in this process is almost beyond imagining. #

"If we change the frequency of the light we shine on the atom by just one part in a billion, the image can no longer be seen," Professor Kielpinski said.

Research team member, Dr Erik Streed, said the implications of these findings are far reaching.

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"Such experiments help confirm our understanding of atomic physics and may be useful for quantum computing," Dr Streed said.

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There are also potential follow-on benefits for biomicroscopy. #

"Because we are able to predict how dark a single atom should be, as in how much light it should absorb in forming a shadow, we can measure if the microscope is achieving the maximum contrast allowed by physics." #

"This is important if you want to look at very small and fragile biological samples such as DNA⁶ strands⁷ where exposure to too much UV light or x-rays will harm the material. #

"We can now predict how much light is needed to observe processes within cells,under optimum microscopy conditions, without crossing the threshold（入口，门槛） and destroying them."#p#分页标题#e#

And this may get biologists thinking about things in a different way. #

"In the end, a little bit of light just might be enough to get the job done." #