Diatomic molecule at a constant temperature

AI Thread Summary
The discussion centers on determining the time evolution of a diatomic molecule, specifically ##D_{2}##, at a constant temperature of 30K, starting from the initial state ##| \psi (0) \rangle = \frac{1}{\sqrt{26}}(3 | 1,1 \rangle + 4| 7,3 \rangle + | 7,1 \rangle )##. Participants consider using the Hamiltonian for a rotator, expressed as ##H = \frac{L^2}{2I}##, but express uncertainty about how temperature factors into the problem. The canonical formalism suggests that the probability of states should follow the relation ##P \propto e^{-\beta E}##, yet there is confusion about integrating this with the rotator model. Ultimately, it is proposed to treat the molecule as an isolated system at ##t=0##, setting aside temperature considerations for the time being. The focus remains on deriving ##| \psi (t) \rangle ## without explicit environmental coupling.
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Homework Statement
All below...
Relevant Equations
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A diatomic molecule ##D_{2}## in ##30K##, in ##t=0##, is in the state ##| \psi (0) \rangle = \frac{1}{\sqrt{26}}(3 | 1,1 \rangle + 4| 7,3 \rangle + | 7,1 \rangle )##, where the kets denote states ##| l,m \rangle##. Use ##\frac{\hbar}{Ic4\pi}=30.4cm^{-1}##.

Obtain ##| \psi (t) \rangle ##

I think the main point here is to deduce what is the Hamiltonian of the system. But i don't know waht could i use!

First i thought it could be a rotator, so ##H = \frac{L^2}{2I}##. But doing so, i am not sure how the temperatura enters in the problem!

It seems that the probability should follows the canonical formalism, so ##P \propto e^{-\beta E}##, where ##P## is the probability of the state with energy ##E##. But how to connect it to a rotator?
(If the rotator idea is correct)
 
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Without an explicit coupling to the environment, there is no way to solve this for the case of constant temperature.

As the molecule is in a pure state at ##t=0##, I would continue treating it as an isolated system and disregard the mention of temperature.
 
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