Post by: chiralSPO on 15/02/2018 22:11:39
atom-big.jpg (184.12 kB . 1863x1863 - viewed 5161 times)The speck of light in the center of the photo is purported to be light being emitted from a single atom. Impressive!
From: http://www.thisiscolossal.com/2018/02/photo-of-a-single-atom/
Post by: Bored chemist on 15/02/2018 22:19:49
Post by: Colin2B on 15/02/2018 23:22:06
This looks like a pinprick of light, we assume he’s right that it only one atom - wouldn’t be hard to fit 2 in there :)
EDIT: Oooo, I say that’s new - those * where i wrote (better not say it again, might get banned!)
Post by: chiralSPO on 16/02/2018 01:58:07
I wonder what got *** out... *****? edit: Yup!
Post by: evan_au on 16/02/2018 11:58:47
The problem with single atoms is that they mostly want to join up with another atom, and then its not a single atom any more; it doesn't resonate at the same frequencies, and the spectrum gets a lot more complicated. You need to keep it in a vacuum chamber.
To get around this, chemists trapped a nitrogen atom inside a C60 "Buckyball", leaving the nitrogen's outer electrons unpaired, but safely locked away so that it can't join up with another nitrogen atom. The internet-style Chemical formula: N@C60.
At GBP 200 million per gram ($US300M per gram), it's a bit more expensive than a naked nitrogen atom, but they hope to make big things of it....
See: https://spectrum.ieee.org/semiconductors/materials/to-build-the-worlds-smallest-atomic-clock-trap-a-nitrogen-atom-in-a-carbon-cage
Post by: chiralSPO on 16/02/2018 14:50:49
At GBP 200 million per gram ($US300M per gram), it's a bit more expensive than a naked nitrogen atom, but they hope to make big things of it....
That's still cheaper than confining the atom in a trap as shown in the picture by several orders of magnitude (on a per-isolated-atom basis)!
Post by: RayG on 18/02/2018 15:27:47
Post by: chris on 18/02/2018 15:45:02
The speck of light in the center of the photo is purported to be light being emitted from a single atom.
I'm not actually sure I can see what they are referring to... can someone "enlighten" me please?
Post by: Bill S on 18/02/2018 19:10:29
Post by: Bored chemist on 18/02/2018 20:01:05
What is seen is the reflection off the atomNo it isn't.
It's a fluorescence emission.
Post by: evan_au on 18/02/2018 21:10:19
Quote from: Bored Chemist
It's a fluorescence emission.Expanding on the comment from Bored Chemist...
In an optical clock, you illuminate the trapped atom (or ion) with a laser beam of the right frequency, which kicks an outer electron into a higher orbital.
- This electron promptly drops back to a lower orbital (not necessarily the one that it came from), emitting one or more photons of specific energy (which means a specific frequency), through the process of fluorescence.
- These photons tend to be emitted in random directions, but if you put a camera close enough for long enough, you will capture enough photons to eventually produce a visible dot.
- If the illuminating laser is focussed well enough, and pointed away from the camera, none of the illuminating laser light will pass directly into the camera.
- Just add a bit of a flash to illuminate the ion trap, and you have a picture of a single atom caught in an ion trap.
https://en.wikipedia.org/wiki/Atomic_clock#Optical_clocks
Post by: chiralSPO on 19/02/2018 01:23:30
No. Because it isnt. Article I read mentions that the picture is a long exposure. The atom is smaller than the actual wavelength of the light. What is seen is the reflection off the atom as it shimmies and moves within the magnetic field. Yes, an impressive photo- but a photo of an atom? No
Clearly the bright spot is much larger than an atom, with a size likely determined by the strength of the confinement. And yes, you are correct that the wavelength of light is much greater than the size of the atom, and this technique would certainly be useless for direct imaging of any atomic structure.
However, I think it is very impressive that they can put enough photons into a single atom that it it could fluoresce (not reflect) enough to be visible to the naked eye. It's basically a single atom filament (surrounded by a very large, expensive, and inefficient light bulb).