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Rotational Quantum Number 0

  1. Mar 7, 2014 #1
    My book on Physics by Beiser specifies that the rotational energy levels of a diatomic molecule are given by J(J+1)/ℏ2, where J = 0, 1, 2, 3, ... .

    However, in the next page, it goes on to mention that the lowest rotational energy level corresponds to J = 1.

    I don't see why that shouldn't be J = 0.

    Any comments would be greatly appreciated.
  2. jcsd
  3. Mar 8, 2014 #2
    Let me rephrase my question.

    I know that the rotational quantum number starts at J = 0,

    but do you count the lowest rotational energy state as J = 0 or as J = 1?
  4. Mar 8, 2014 #3


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    J = 0 is the ground state. J = 1 is the first excited rotational state.
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