Rotational Energy and Degeneracy

In summary, the rotational energy equation is derived based on the rigid rotor assumption and is expressed as ##\epsilon = k\theta_r J (J+1)##, where k is the Boltzmann constant and J is the rotational quantum number. The degeneracy of this equation is 2J+1, but assuming a constant quantity of ##k\theta_r## = 1 and an energy level of 2 Joules, the only physical solution is J = 1, giving a degeneracy of 3. This is because there are three linearly independent solutions to the Schrodinger equation with ##J=1##, represented by the three functions ##Y^1_m## with ##m## equal to
  • #1
pyroknife
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I have a question regarding the rotational energy equation, derived based on the rigid rotor assumption:

##\epsilon = k\theta_r J (J+1)##
where k = Boltzmann constant, and J is the rotational quantum number.

The degeneracy is 2J+1.

Let's assume the constant quantity ##k\theta_r## = 1 and that the energy level is 2Joules.
Thus 2 = J(J+1) => J = +/- 1. The only physical solution is J = 1.
Thus degeneracy is 3 for J = 1.

Here is where I am confused. I thought degeneracy is when you have an energy level that DOES NOT consist of a unique set of quantum numbers. So if the degeneracy is 3, doesn't that mean I should have 3 different J values that can give me an energy level of 2 Joules?
I think I am understanding this incorrectly, because for 2 joules, the only solution is J = 1. Doesn't that mean the degenearcy is 1?
 
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  • #2
There are three different and linearly independent solutions to the Schrodinger equation with ##J=1##. That's where the three-fold degeneracy comes from.

Google for "spherical harmonics" to see how this can be; the three solutions are multiples of the three functions ##Y^1_m## with ##m## equal to -1, 0, or 1.
 

FAQ: Rotational Energy and Degeneracy

What is rotational energy?

Rotational energy is the energy associated with an object's rotation. It is a form of kinetic energy and is dependent on the object's mass, radius of rotation, and angular velocity.

How is rotational energy calculated?

The formula for rotational energy is E = 1/2 * I * ω^2, where E is the rotational energy in joules, I is the moment of inertia in kg*m^2, and ω is the angular velocity in radians per second.

What is degeneracy in rotational energy?

Degeneracy in rotational energy refers to the phenomenon where multiple energy states have the same energy value. This occurs when there are multiple ways for an object to have the same amount of rotational energy.

How is degeneracy related to the quantum mechanical nature of rotational energy?

In quantum mechanics, rotational energy is quantized, meaning it can only exist in discrete energy levels. Degeneracy occurs when multiple energy levels have the same energy value, which is a result of the quantization of rotational energy.

Can degeneracy be observed in real-world systems?

Yes, degeneracy can be observed in real-world systems. For example, in molecules, different energy levels can result in the same rotational energy value. This allows for multiple possible energy states for a molecule, making it more stable and less likely to break apart.

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