What is the relationship between reabsorption and heating in laser cooling?

In summary, the conversation discusses the concept of laser cooling and the Doppler limit on temperature. The speaker is having trouble understanding how emission can heat an atom and asks for an explanation. The response mentions that reabsorption of spontaneously emitted photons can cause heating, leading to an increase in equilibrium temperature with higher density and number of atoms. The speaker still does not understand why reabsorption causes heating.
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Homework Statement


I have to study laser cooling. I'm actually trying to understand the Doppler limit on temperature.
On the net I have found "at a certain point the cooling mechanism is foiled by heating due to the random absorption and reemission of photons. (http://hyperphysics.phy-astr.gsu.edu/hbase/optmod/lascool.html)" (A similar sentence is in Phillips' Paper "Laser cooling and trapping of neutral atoms")

I can't understand in which way emission can heat the atom... Can you explain me? A lot of thanks
 
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  • #2
In this paper http://users.phys.psu.edu/~dsweiss/PRA%20RC%20laser%20cooling%20in%20optical%20lattices.pdf it says: "Laser cooling requires spontaneous emission,
and spontaneously emitted photons can be reabsorbed by other atoms. Reabsorption causes heating, which makes equilibrium temperatures increase with the density and number of atoms".

I don't understand why reabsorption causes heating...
 
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Related to What is the relationship between reabsorption and heating in laser cooling?

1. What is laser cooling?

Laser cooling is a technique used to slow down the movement of atoms or molecules in a gas using laser light. This allows for the study of individual atoms and molecules and their behavior at very low temperatures.

2. How does laser cooling work?

Laser cooling works by using a combination of laser light and magnetic fields to manipulate the energy levels of atoms or molecules. The laser light is tuned to a specific frequency that corresponds to the energy difference between two levels of the atom, causing it to absorb and emit photons and lose energy in the process. The magnetic fields then trap and confine the cooled atoms in a specific region.

3. What is the Doppler limit in laser cooling?

The Doppler limit is the lowest temperature that can be achieved through laser cooling, and it is determined by the spread of velocities of the atoms being cooled. This limit is a result of the Doppler effect, which causes the frequency of light to shift when observed from a moving source.

4. What are the applications of laser cooling?

Laser cooling has many applications, including atomic clocks, precision measurements, and quantum computing. It is also used in the study of ultracold atoms and quantum gases, which can provide insights into fundamental physics and help create new materials with unique properties.

5. What are the limitations of laser cooling?

The main limitation of laser cooling is the Doppler limit, which prevents temperatures from reaching absolute zero. Additionally, laser cooling is only effective for certain types of atoms and molecules, and it requires specialized equipment and expertise. It is also a slow process and can only cool a small number of particles at a time.

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