Potential Energy/ dipole moment curves

In summary, the conversation revolved around creating a potential energy curve and its relation to a dipole moment curve, as well as extracting information from these curves. It was mentioned that solving the many-body problem using the Schrödinger equation is necessary for theoretical calculations, while a fitting procedure is needed for experimental results. The conversation also delved into the use of the Born-Oppenheimer approximation and the eventual goal of creating a Molecular line list through theoretical calculations.
  • #1
jl29488
10
0
Hi,

I wasn't sure if this is more Physics/Astro or chemistry because its actually all 3.

i've got some conceptual issues with some tasks at hands, and was wondering if anyone could clear that up for me.

(These questions are all regarding molecules)

1) How do you create a potential energy curve? What are the core ingredients? (quantum numbers etc..?)
2) How does a potential energy curve relate to a Dipole moment curve.
3) What can you extract from these curves?

Thanks so much!
 
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  • #2
jl29488 said:
1) How do you create a potential energy curve? What are the core ingredients? (quantum numbers etc..?)
Theoretically, you need to do some quantum chemistry, basically solving the many-body problem (nuclei + electrons) using the time-independent Schrödinger equation. By varying the distance between the atoms, you get the variation of the energy as a function of that distance, resulting in the potential energy curve. Experimentally, you need some fitting procedure, where manipulate a potential energy curve until it produces the correct set of observed levels.

jl29488 said:
2) How does a potential energy curve relate to a Dipole moment curve.
It doesn't. You can extract the dipole moment from the same quantum chemistry calculations. I'm not sure how you get the dipole moment from experiments, but I guess it is related to line strength.

jl29488 said:
3) What can you extract from these curves?
A lot of what you want to know about the properties of the molecule.
 
  • #3
Thanks for the reply.

Would I not solve the Schrodinger equation for the electrons and nuclei separately (Born oppenheimer approx) ?

Also, how can I extract the rotation-vibration wave functions and energies for solving for the motion of the nuclei/electrons?

Sorry if this my questions don't sound particularly ordered. I am just trying to create a mind map of how its all interlinked.

The eventual goal is to create a Molecular line list.
 
  • #4
jl29488 said:
Would I not solve the Schrodinger equation for the electrons and nuclei separately (Born oppenheimer approx) ?
The nuclei are still there, just not moving! I didn't mention the BO approx explicitly, but it is what I was referring to in saying "varying the distance between the atoms."

jl29488 said:
Also, how can I extract the rotation-vibration wave functions and energies for solving for the motion of the nuclei/electrons?
Once you have the potential energy curve, you can solve the Schrödinger equation for the motion of the nuclei, and get ro-vibrational states.
 
  • #5
jl29488 said:
The eventual goal is to create a Molecular line list.
Do you mean you want to theoretically calculate a series of lines, in order the be able to identify actual spectra? If that is the case, good luck! Producing work good enough to compare to experimental values is not a trivial task.
 

1. What is potential energy?

Potential energy is the energy possessed by an object due to its position or configuration. It is a measure of the work that can be done by a force on the object as it moves from one position to another.

2. How is potential energy related to dipole moment curves?

Dipole moment curves are graphical representations of the potential energy between two electrically charged particles as a function of their separation distance. The potential energy is directly proportional to the dipole moment, which is a measure of the separation and magnitude of the charges.

3. What factors affect the shape of a dipole moment curve?

The shape of a dipole moment curve is determined by the charges and their separation distance. It is also affected by the dielectric constant of the medium, which describes how well the medium can store electrical energy.

4. What is the difference between potential energy and kinetic energy?

Potential energy is stored energy, while kinetic energy is the energy an object possesses due to its motion. Potential energy can be converted into kinetic energy and vice versa.

5. How is the concept of potential energy used in practical applications?

Potential energy is used in a variety of practical applications, such as in physics experiments, calculating the energy in chemical reactions, and designing structures that can withstand potential energy changes, such as roller coasters and dams.

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