
Physicists captured individual atoms and observed them merge into a molecule - martonlanga
https://www.otago.ac.nz/news/news/otago732837.html
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JeremyHerrman
For those wondering about why the article says "Two atoms alone can’t form a
molecule, it takes at least three to do chemistry", here's another explanation
from the reddit thread [0]

> Each atom has some amount of energy associated with it. If you just bring
> two atoms together, the total energy is simply the sum of their individual
> energies. This state is typically referred to as an excited state. However,
> the stable bonded form of the two atoms actually has a lower energy. So to
> go from two separate atoms to two bonded atoms, the atoms have to first
> collide and form the excited state and then lose some amount of energy to go
> to the stable state. If they don’t lose that energy, then they can and will
> break apart again. One way to lose that energy is via collision with the
> third atom.

> In normal systems where you have tons of atoms flying around, collisions
> happen very frequently, so you can typically assume that the stabilization
> will happen immediately following the reaction. This is why the idea that
> stabilization is an important step in a chemical reaction is typically not
> covered in intro chemistry. However, it’s not uncommon to have conditions
> where that assumption does not hold. This then gets into the concept of
> pressure dependent reaction kinetics, which studies the effect of having
> slow stabilization.

[0]
[https://www.reddit.com/r/science/comments/f7mqwl/physicists_...](https://www.reddit.com/r/science/comments/f7mqwl/physicists_captured_individual_atoms_and_observed/)

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sfifs
Interesting. Is this how catalysts work? By bringing the atoms/molecules
reacting together and providing a path for taking away the excess energy more
easily?

~~~
mensetmanusman
We still don’t know exactly how catalysts work, because they operate at high
temperature and pressure, so it is very hard to study.

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Ao7bei3s
That doesn't seem right. Cars have catalysts where the air flows through. Also
2 H2 + O2 -> 2 H2O (+ a characteristic bang :-)) at room temperature and
pressure (initially) using a platinum catalyst is shown in school chemistry
classes.

Just learned on Wikipedia (en/Platinum) that the 2007 Nobel price in Chemistry
was awarded for explaining how that works. doi:10.1002/anie.200800480

~~~
pritovido
Car's catalyst work at high temperatures, not at room temperature.

In fact, at room temperature they don't work at all, which is exactly the
problem with catalysts, they don't work when you start your car.

They need to heat with the hot combustion gases to start working, and that
takes a while.

This is one of the reasons that laboratory's measurements of particles and
gases like nitrogen oxides do not apply to real emissions in cities, because
most people in cities will use the cars, for example, diesels in Europe, for
very short periods of time, then let the car cool down and use it again to go
back less than 10 kilometers away.

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jeherr
There are many kinds of catalysts beyond materials surfaces. Organic chemists
use metal complexes as catalysts in organic synthesis. This is especially
important in asymmetric catalysis where you want to form high excesses of one
isomer of a molecule, which can have drastically different effects in medicine
for example. Catalysis also plays an important role in biology I believe.

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martonlanga
Interesting discussion on reddit:

> It appears you need the energy from 3 in order for the 2 to make a bond.

> It's the other way around. Two atoms alone will release a bunch of energy
> when they form a molecule; exactly enough energy to rip the molecule back
> apart. That energy has to go somewhere, and where it goes is the third atom.

~~~
doubleunplussed
Yep, this is spot on.

In other atomic physics experiments it's a problem - three-body collisions are
able to dump energy into one of the three atoms and that atom has enough
energy to escape the trap. These are "three-body losses".

Whereas with two-body collisions, neither atom can be going any faster
afterwards than the fastest one was before the collision. So they remain
trapped.

Since the three-body collision rate is proportional to the cube of the density
of atoms, and the two-body collision rate only to the square of density (for
obvious reasons), this phenomenon limits the density of atomic clouds we can
do experiments with. If we increase the density to the point where three-body
collisions are significant, we rapidly lose atoms.

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iandanforth
I love how much of science is "We built a thing to look more closely at things
and now we know more!"

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wruza
Can someone please comment on the picture? What is bottom-righty part, which
looks like some device?

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nyc_pizzadev
Simplified version with graphic:

[https://physics.aps.org/synopsis-
for/10.1103/PhysRevLett.124...](https://physics.aps.org/synopsis-
for/10.1103/PhysRevLett.124.073401)

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panic
Here’s an arXiv link if you’re hitting a paywall on the paper itself:
[https://arxiv.org/abs/2001.05141](https://arxiv.org/abs/2001.05141)

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basicplus2
Pity there are no images of the merge occuring..

