Calculating the Bose-Einstein Condensation Temperature

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SUMMARY

The discussion focuses on estimating the Bose-Einstein condensation temperature of Rb 87 atoms with a density of 1011 atoms per cm3. The formula used is T = (n2/3h2) / (3mKB), where the user initially encountered issues with unit conversions, leading to unrealistic temperature results. After identifying the error related to the squared Planck constant, the user recalculated and successfully obtained a final temperature of 16 nK, which aligns with expected values for a Bose-Einstein condensate.

PREREQUISITES
  • Understanding of Bose-Einstein statistics
  • Familiarity with the Planck constant and Boltzmann constant
  • Knowledge of unit conversions between eV and Joules
  • Basic principles of quantum mechanics and atomic physics
NEXT STEPS
  • Study the derivation of the Bose-Einstein condensation temperature formula
  • Learn about the properties of Rb 87 atoms in quantum systems
  • Explore unit conversion techniques in physics calculations
  • Investigate experimental methods for observing Bose-Einstein condensates
USEFUL FOR

Students and researchers in physics, particularly those focusing on quantum mechanics, atomic physics, and statistical mechanics, will benefit from this discussion.

Mr LoganC
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Homework Statement


Estimate the Bose-Einstein condensation temperature of Rb 87 atoms with density of 10^11 atoms per cm^3.


Homework Equations


T=\frac{n^{2/3}h^{2}}{3mK_{B}}


The Attempt at a Solution


This should be just a standard plug and chug question, but my answers are not even close to reasonable! I would expect to get anywhere from 500nK to 50nK for an answer, but I am getting thousands of Kelvin! Are my units wrong? I am using Boltzmann constant with units of eV\bullet K^{-1} and Plank's with units of eV\bullet s.
Then I am using the density in Atoms per m^3 and the mass of a single Rb 87 atom in Kg.
Am I missing something here with units? That is the only thing I can think is wrong.
 
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At first glance I would use joules (Nxm) instead of eV since since other units are SI...
 
bloby said:
At first glance I would use joules (Nxm) instead of eV since since other units are SI...

But since the plank constant is on the top and Boltzmann on the bottom, the converting factor of eV to joules (1.6x10^-19) would cancel out anyway, so whether it's in eV or Joules should not matter.
 
Mr LoganC said:
But since the plank constant is on the top and Boltzmann on the bottom, the converting factor of eV to joules (1.6x10^-19) would cancel out anyway, so whether it's in eV or Joules should not matter.

Actually, that IS the problem! I think you are correct, Bloby. Because the Plank constant is squared on the top, so there is still another 1.6x10^-19 to factor in there! I will give it a shot and see what I get for an answer!

****
It Worked! Thank you Bloby! Final answer was 16nK, which seems pretty reasonable to me for a Bose-Einstein Condensate.
 
Last edited:

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