Cooling with Light! Zeeman, Laser, Chirp and Doppler Cooling Explained

[@Kathy_Loves_Physics]

Excellent job! Fun fact, Zeeman discovered Zeeman cooling because he read that Faraday tried it as Faraday’s last experiment like 50 years previously. Zeeman tried it with better equipment and voila Nobel for him and for many others too.

[@nachiketakumar9645]

Wow, mam i wondered. Plz mam make a video on the above topic. Love from India 🇮🇳

[@Ritefita]

So, it's a Nobel for having a means of production.

[@gabrielevensen5755]

Amazing video!!! Thank you!! This helped me so much. Explaining these topics in a way that we can actually visualize what is happening even at the atomic level is so incredibly helpful for visual learners like me. And the diagrams and animations you made to go with it are top notch. Hope you keep making these videos and Thanks again :)

[@kevinhevans]

YES. We went over this in my atomic class and I was lost the entire time. I finally understand it now! :)

[@enotdetcelfer]

Just found your channel, how do you only have 2K subs duuude. Do you have monetization turned off or something? Going to go through your uploads and watch everything, glad to see you're still making vids, good stuff!

[@dhruvg550]

Very well explained! For a moment I felt like I was watching a Khan Academy video!

[@atomsandsporks6760]

Hi praise! Thanks

[@rehansiddiqi2967]

Thanks. You explained a great deal and covered a number of events in a highly comprehensive manner, that too in only 19:55. Kindly make a video of nK cooling by evaporating atoms from a magnetic bottle.

[@dnh4eva303]

Awesome video ! Awaiting the basics of nanoplasmonics one : )

[@atomsandsporks6760]

Uh oh, busted.... Ya, I am working on that. The thought process of why I didn't immediately do the third video was that I didn't want to become "the nanoplasmonics guy" and I also saw a steep drop-off in interest after the second part. But I definitely will get back around to it.

[@jxnnzm2986]

This is an very good explanation, I've had 2 uni lectures that didnt make it as clear as this video did!

[@divyanshtripathi5037]

Amazing video man!!

[@abhishekbhardwaj1603]

This video is awesome! One of the best and simplest explanation I could find. Will you make a video on MOT's in continuation to this topic?

[@aquariandragonhare8953]

Yes Jake Hensley! That is a great idea

[@Ritefita]

At the end you wrote "we learned about... .. detuRned lasers =) Great video. Thanks.

[@joxa6119]

Thank you for saving me from my Atomic Physics course in this miserable 2020.

[@jeremykeetch7213]

Great explanation

[@aizuddinahmadkamely3402]

I don't know if you still read the comments here. But about the doppler cooling at 16:16, how can the atom absorbs the laser frequency (having momentum to the right) when the laser frequency is lower than the atom resonance frequency at the first place?

[@dukefbfan5013]

Sorry, maybe I'm wrong, but Doppler cooling still doesn't trap atoms that effectively to my knowledge. There is still significant "walk" of atoms due to random emission as you mentioned. And that "walk" is usually such that the velocity of the atom is not high enough to bring the laser back on resonance with the laser. Within some velocity limit, the atoms are trapped (which is why this can tap atoms on the minute scale), but we know that this is also slowing the atoms, so the velocity lowers to the point where the doppler shift will no longer be on resonance. So once the atoms are sufficiently cooled, they are also, unfortunately, not trapped.

[@sssssnake222]

I wonder if it could be used on a large scale, say to stop a hurricane?

[@abcdef2069]

at 6:32 even if absorption is directed, reemision is in all directions. something is not right about the animated movement. 1st i related this to compton scattering. your dx and dp are too precise simultaneously. maybe your target matter is not an atom but it may be a heavy macroscpic matter. so all side scatterings are too weak and ineffective compared to many incoming photons' forward momentum.

[@Yash-Gaikwad]

So true, no one is talking about this. I never heard of spontaneous emission in all directions. It is always a random direction. If it were emissions in omni- direction the laser would never work.

[@theclerk3163]

How does the color white differ in wavelength reflectance from what is emitted from a mirror?

[@rbkstudios2923]

6:25 But how can atoms radiate light isotropically if a single photon is coming into action Please answer

[@rbkstudios2923]

@Roberto Iannuzzi Um... Okay... Can you provide a reference link for this?

[@rbkstudios2923]

@Roberto Iannuzzi Thanks

[@atomsandsporks6760]

If one wants to think in terms of photons then the absorption and emission events are separate events and when it comes to the emission event the probability for the photon emitting in any given direction is the same (emission probabilities are spherically symmetric and isotropic). So on average after many emissions there will be no net effect in any one direction.

[@rbkstudios2923]

@@atomsandsporks6760 But doesn't that violate the conservation of momentum If you have an isolated system with a photon moving towards an atom, it is absorbed by the atom and remitted into a different direction.

[@atomsandsporks6760]

@@rbkstudios2923 There's no violation, for ever absorption and emission there is a recoil, it's just that absorption is only happening from one direction and so all the recoils are in the same direction and thus every absorption event results in a net momentum change. Say the laser photons are moving to the left. Every absorption then gives it a kick to the left. It then reemits, if it reemits perfectly to the left it'll get a kick back to the right and be slowed back down, but it's equally likely it emits to the right, in which case it actually doubles its speed, the avsrage of those two possibilities? The reemission does nothing. It can also emit upwards or downward and either would give it a kick in the respective opposite direction but it does both with equal probability and so again there is no net effect. Imagine you're a hockey player on ice and someone keeps launching pucks at you from the same direction over and over knocking you back more and more along that direction, But when you receive a puck you launch it away.. but in a totally random direction, the net result would just be you pushed back. Or a gunslinging octopus with a little handgun attached to each if its many tentacle and it points out all its gun tentacles, equally spaced, in all directions and pulls all the triggers at one. Whch direction is he recoiled? No where.

[@KWifler]

Do you think an amateur could create a laser contraption that would somehow cause a cooling effect in its target? Or at least something that's not too expensive to put together? Not necessarily this exact concept, but something with lasers? Thanks.

[@atomsandsporks6760]

I'm really sorry, but I honestly couldn't say. I'm a theorist who pushes pencils and paper and computer code around. I can certainly appreciate these great experimental achievement but I'd be absolutely useless to actually try and perform one. You might want to check out the KZbin channel "Applied Science". He does some pretty ambitious physics experimentation and some definitely involves lasers.

[@Ritefita]

Try to search video "the real double slit ...". - the guy made enough.

[@jonathanwhite3507]

We need a point of heat opposite the 0°k level. Push pull with the new design of warp drive.

[@godfreyw5412]

This video is gold

[@amintaremi3329]

Great Video, Thanks a lot.

[@fehmi35]

great video but confused myself too much, please help. something. When the photon is absorbed, it means that an electron of the atom is excited. So, I guess the energy and the momentum of the photon does not fully passes only to the electron because center of mass of the atom slows down, right? So how much of the momentum passes to the electron and the center of mass of the atom ? I mean I am really confused about how the momentum is conserved since electron in higher level gains momentum and energy but overall whole atom slows down. so does this electron has a directional momentum that slows down the whole atom ? Also when the light is re-emited, atom gains its energy back by recoil even average momentum is zero, it still has the same energy , no ? How does it gets cooler if the energy is conserved. I need help, I am super confused.

[@bhoopendragupta4782]

Very informative and easy to understand. Thanks

[@dysteleological]

Great video.

[@shyamaugustine7272]

Wouldn't the laser used here have a lower frequency than the resonant frequency than the atom? Am I missing something?

[@lorisfoucart2475]

I'm probably making jibberish but I'd like to know why. If we found the frequency of light needed to push off of dark matter or ultrared lights scattered in the universe (or something 😅), could we produce thrust by blasting the said frenquency at it ?

[@nachiketakumar9645]

Please make more videos

[@MaryamMful]

Thank you very much. Did you do a follow-up video on Claude Tannoudji's contribution or sub-doppler cooling techniques?

[@atomsandsporks6760]

Not yet, unfortunately. Perhaps some time in the future though.

[@rbkstudios2923]

Superb work I had seen these on other channels But they rather grazed the topic and they didn't explain the most logical and basic phenomena of atoms radiating isotropically I'm o looking forward to these kinda video which cover a topic from basic level 👏👏 You've appreciation from India But who are you, I didn't find anything about you in KZbin About section

[@atomsandsporks6760]

Thanks!

[@rbkstudios2923]

@@atomsandsporks6760 Hey It's completely alright if you don't wanna reveal your identity But I've got a list of topics on which you can create videos (these should be of your liking) 1. Negative Temperatures 2. Gravitational waves property. If they travel at light speed, do they have other similar properties like reflection, refraction, diffraction, doppler shift polarization. What is their wavelength range? does special relativity apply to it? 3. Collapsing an air bubble with sound underneath a liquid surface 4. Doppler shift of a single photon 5. Dynamo Effect

[@jonathanwhite3507]

We can't do warp drive yet.

[@oliviaheuts3479]

Such a great video! Thanks! I was wondering about the laser cooling, wouldn't the laser only be able to slow down atoms of a certain speed? Isn't is possible that the photon would be too energetic for the atom to absorb if the atom is moving too fast against the laser?

[@atomsandsporks6760]

Well that's why you need to chirp or Zeeman shift during flight. Otherwise the atomic resonance passes out of the laser's frequency bandwidth.

[@SyroccoModding]

Very informative thanks!!!

[@da2015]

Fantastic

[@gene4094]

Also for superconductive nano particles for water splitting…

[@bravo498]

Great video! Thanks!

[@Bucciarello]

Thanks this was very clear; I just have a question: I agree that a right-moving atom might absorb the left laser and be transparent to the right laser, but wouldn't the opposite be true for a left moving atom? And in a gas of atoms, being the distribution of velocities isotropically distributed, wouldn't the two effect cancel out? Do we polarize the atomic motion in some way? EDIT: no ok I just realized X-D

[@das250250]

What if the gas could be surrounded by an array of lasers in a sphere pointing inward where all light focuses on a single point in space

[@strivvy6852]

Could this be used on mass scale to freeze someone like what Captain Cold does?

[@atomsandsporks6760]

These approaches only work on gases that have already been super-cooled by some other approach (i.e. they take it from the "few Kelvin" range to the "nanoKelvin" or further). I kinda always assumed Captain Cold just shot liquid nitrogen or something :). Though it's worth pointing out one actually *can* cool a solid at room temperatures using light, through something called "optical refrigeration", but this requires the material to be specifically engineered to be cooled in this way.

[@Yash-Gaikwad]

You are wrong! In many of your videos. In this perticular... 6:32 I never heard of atom spontaneous emission in all directions. Spontaneous emission always has a random direction. It is just not possible for a single photon to be emitted in all directions. Laser would not have been a thing if your physics is applied. If I am wrong please explain in detail

[@nirorit]

EE student here, what courses do I need to take to get a better grasp of this subject? My physics education has ended with basics in quantum mechanics.

[@dhruvg550]

I think Photonics & Lasers and Atomic Physics should help. Maybe look around at MITOCW

[@atomsandsporks6760]

If you just want to learn a bit more than I'd recommend the Physics Today articles "Laser Cooling" by Wineland and Itano and "New Mechanisms for Laser Cooling" by William D. Phillips and Tannoudji themselves. These were the original inspiration for the video. There is also a quasi-approachable Review of Modern Physics by William D. Phillips called "Laser cooling and trapping of neutral atoms". If you want to go deeper, I second everything Dhruv Gupta said. If you care about the cold atoms that's generally called Atomic, Molecular Optical (AMO) physics. If you care about the lasers that's generally photonics.

[@DaybreakSystem-x8q]

I keep inventing things and then looking for them and finding out they've all been invented already.

[@learningcurve823]

9:55 the scripts maybe the opposite

[@ChiDraconis]

You will need some coffee to read this: The work is © Space Lizards This looks very appealing: Working on Quantum Chirping I consider spectral dispersion of EM ( light a/k/a fermion ) Given a Riemann surface as a 2-point vector sampled from an n-body Riemann surface taking Fine Structure Constant as some limiting value not within the capabilities of my vocabulary and nomenclature we take an emission in any arbitrary "Vector space" with the constraint this "vector space" is an event-taken as reduced model-of the "one-dimensional complex manifold" facetiously modeled as "Cleere" ( our investigator ) is attempting to contact "Orinda" → a "Long lost decedent relative" in a which occurs at *T(arbitrary)* → future event · after a few billion spent at CERN vacation resort Meyrin waiting for an idealized event our investigator team realizes this is available as a standard textbook case the "energy" ( defined as you wish ) splays-to spread out or widen-with tighter compressive effects primarily aligned in what most would take as the longitudinally forward direction of the 2-point Cleere → Orinda with forward *{ ± }* time noted as *+* by convention ~ proceeding thus the backfield from Orinda should display the Axial bias seen in COBE & related experiments → *Speculatively* a planar radius at an instant taken from the propagation of the wave-particle sufficiently narrow sample time to detect anything this side of FSC ( tangible or hadronic ) should based on what I have found so-far display a neutral "zone" at Θ ~ 90 ° ( "∟" orthogonal to the one-dimensional Cleere ↨ Orinda ) such that spectral dispersion spreads or broadens ( Zeeman / Stark effect ) due to gravity between physicality but since our model does not specify Orinda to be present in time now we can simplify as bench experiment using standard tools where we would see emissivity in spheroidal form such that ±Time displays hysteresis as given in: *Maslovski, Stanislav & Simovski, Constantin & Tretyakov, Sergei 2014* _Overcoming black body radiation limit in free space: Metamaterial super emitter_ New Journal of Physics. 18. 10.1088/1367-2630/18/1/013034.

[@ChiDraconis]

See also: *"Evidence of Radial Nulls Near Reconnection Fronts"* {doi.org/10.3847/1538-4357/aafa16}

[@OrphanRed]

You deserve more subscribers! Are you advertising your channel on other social media platforms? Have you tweeted your favourite/best one to physics Twitter accounts with a clever snippet to draw the attention of that account's followers? I think you should. I will for you as well, but I don't have much influence on Twitter. I just hate to see KZbin granting success to Jake and Logan Paul while videos like yours are not as widely shared as they should be. :)

[@atomsandsporks6760]

I'd be lying if I said that I wasn't largely fumbling around in the dark with all this, but my near-term mind-set is to simply work on developing a library of content. Sadly it takes me ~1 month to make these video with 70% of that just being the visuals. After a certain point though I should probably start making stern grown-up decisions about how to grow things. But for now it's mostly "thoughts to paper" then "paper to video" and then hit the "add video" button.

[@Ritefita]

I thought it's impossible to take out the energy from the matter by sending a lot of energy there. Ok. Quantisation gives us ways to cheat