# Questions tagged [cold-atoms]

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### How is the pressure derived from the Gibbs-Duhem equation, within the Local Density approximation? (Problem in calculating an integral)

Following this reference https://www.nature.com/articles/nphys1477.pdf (starting from Eq 3), I am trying to understand the details in the derivation of the pressure along the x axis p(x,y=0,z=0) from ...
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### Calculating the Feshbach resonances between carbon atoms

From my understanding, Feshbach resonance is a scattering resonance that occurs when the energy of an atom pair coincides with the energy of a molecular bound state. Feshbach resonances are ...
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### Question about the energy levels of Rubidium atom - how to understand this energy level diagram?

But today when I try to read some papers working with Alkaline atom, I couldn't figure out how they plot the Rubidium energy level. From my undergraduate study, I thought the diagram of Rubidium atom ...
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### Phase space density for Bose-Einstein condensation

A figure of merit for Bose-Einstein condensation is the phase space density which can be defined as $$\rho=n\lambda_T^3,$$ where $n$ is the number density of atoms and $\lambda_T$ the thermal de ...
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### Confusion over Feynman’s description of the Wu experiment for parity violation

In his lecture on symmetry in physical law, Feynman said: Using a very strong magnet at a very low temperature, it turns out that a certain isotope of cobalt, which disintegrates by emitting an ...
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### How is two-level optical transition in a spin 1 system affected by the third level?

Suppose you have a spin-1 system. Let us resonantly drive the transition between any 2 levels (say 0 1 transition). How would the the presence of the third level (-1) state affect this transition? We ...
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### What wavelengths are used practically in optical trapping?

I am currently working on my Master thesis in a cold atom research group, and have irritatingly found -- or rather not found -- that no book or paper seems to explicitly mention what wavelengths are ...
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1 vote
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### What is the longest wavelength ever measured for a Black Body?

As said in the title, I am curious about the reported measurements for cooled black bodies. Any source is welcome. I am neither interested in any thought experiment nor in the well-established law of ...
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1 vote
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### Any introductory books/articles on ultra-cold atoms?

I am currently only a high school student wanting to pursue physics at the tertiary level of education. Are there any books people can recommend on ultra-cold atoms? I would like to discover more ...
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### Using an electric/magnetic field to cool particles

I was just thinking that temperature and the motion of atoms are connected. Hence, I was wondering why we can’t just use a magnetic or electric field to hold atoms more or less in place, lowering ...
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### What is a good definition for what this article talking about when it refers to "Universal Physics"?

I was puzzled when I read "Precise measurements find a crack in universal physics by Ingrid Fadelli" (Phys.org, Jan. 15, 2020). The article has some vague statements in the opening paragraphs about "...
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### Transitions within magnetic sub levels: evaporative cooling to Bose Einstein Condensation

Consider a Ioffe-Pritchard trap geometry. Evaporative cooling works by decreasing the trap depth to remove atoms which are more energetic than average; this leads to cooling. This is done by using ...
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### What is the classical counterpart of ultra-cold atoms?

I'm studying quantum chaos in ultra-cold atoms. However, quantum chaos denotes the quantum mechanics of classically chaotic systems and it is not clear to me what is the classical counterpart of ...
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### Does the size, and distance between, expanding ultracold gas clouds depend on the populations in each cloud?

Say you had some $^{87}$Rb atoms at a few kelvin and you knew that the atoms were distributed among the magnetic sub-levels of a hyperfine manifold. You want to know the relative population of each by ...
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### Why is the density of a BEC so low?

I've just begun reading C. Pethick and H. Smith's textbook "Bose-Einstein condensation in dilute gases" (Cam. Uni. Press). In the Introduction, they contrast the density of atoms at the centre of a ...
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### How are atoms formes by electromagnetic waves that a specific frequency? [closed]

I came up something like this- Every piece of matter has a resonancefrequency or series of frequenciesbecause all matter is made up of atoms. Atoms are formed by electromagnetic waves that have a ...
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### Is it BEC-BCS crossover the natural framework to explain superconductivity from ultracold atoms?

I know that superfluidity and superconductivity have very distinct characteristics and have specific theories. However, it seems that in ultra-cold atomic gases these phenomena can be understood by a ...
166 views

### speed of freezing vs. moving [closed]

An idea came to my mind and like to discuss it. We know that out there in the space the absolute zero (aka. -273 C) is almost reached where all the particles and atoms would freeze up and stop giving ...
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### In AMO experiments, how do cold alkali metal atoms remain gaseous?

My focus is on condensed matter physics, so I've never really explored this question although it always seemed curious to me. My "immediate reaction" intuition would dictate that cold metal atoms ...
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### What laser frequency is needed for the Doppler cooling of iron?

What laser frequency is needed for Doppler cooling iron? How do you determine this frequency?
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1 vote
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### Energy conservation in Kapitza-Dirac diffraction?

In Kapitza-Dirac diffraction, a standing wave of light (wavevector of single wave $k$) is pulsed on for a very short period of time ($\sim \mu s$) onto a bunch of cold atoms. This results in the atoms ...
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### Polarization of light and transitions in a Magneto Optical Trap

After reading this question, I realized that I didn't really understand how a MOT works in detail. I was always relying on the simplistic picture given in textbooks which never addresses the actual ...
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### When are two fermions considered identical?

I am a bit confused about the terminology concerning identical fermions. In quantum mechanics, identical fermions need to obey certain anticommutation relations i.e. have an antisymmetric total ...
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