I Questions about Franck-Condon principle

  • I
  • Thread starter Thread starter Salmone
  • Start date Start date
  • Tags Tags
    Principle
Salmone
Messages
101
Reaction score
13
I have some questions on Franck Condon principle:

1. The principle states that if a molecule absorbs a photon of the appropriate energy, we could have both electronic and vibrational transitions and that is more likely to have a vibrational transition between states that have two "similar" wavefunctions. The first question is:
It is ok to me that it is more likely to have a vibrational transition between states that have two "similar" wavefunctions but of course if we see a transition between ##\nu=0## state and ##\nu'=5## state means that the absorbed photon had at least the energy separating ##\nu''=0## and ##\nu'=6##, right? With reference to the image, the "blue arrow transition" is more lilely to happen but we need a photon with the right energy, more or equal to the "lenght" of the arrow, right?

2. If the energy of the incoming photon is enough for that transition, is it mandatory for the molecule to also have a vibrational transition or it can jump just from electronic G.S. to electronic first excited state remaining on the same vibrational level?

3. Again with reference to the image, the potential drawn higher refers to an excited electronic state, if we are talking about molecules, what do we precisely mean by that? If just one electron of the electronic clouds is excited by a photon, the new arrangement of the molecule need to be drawn higher than the ground state in which all electrons were in their ground states? And, if two photons are excited, the new potential must be drawn as a different one much higher? Same if three electrons are excited or two electrons are excited to second excited state or third excited state?

800px-Franck_Condon_Diagram.svg.png
 
Last edited by a moderator:
Physics news on Phys.org
Doubts meaning you do not think it works like that or that you don't understand that principle?
 
malawi_glenn said:
Doubts meaning you do not think it works like that or that you don't understand that principle?
I don't understand the points I've written
 
Salmone said:
I don't understand the points I've written
You have questions. You should write questions instead of 'doubts'.
 
Insights auto threads is broken atm, so I'm manually creating these for new Insight articles. Towards the end of the first lecture for the Qiskit Global Summer School 2025, Foundations of Quantum Mechanics, Olivia Lanes (Global Lead, Content and Education IBM) stated... Source: https://www.physicsforums.com/insights/quantum-entanglement-is-a-kinematic-fact-not-a-dynamical-effect/ by @RUTA
If we release an electron around a positively charged sphere, the initial state of electron is a linear combination of Hydrogen-like states. According to quantum mechanics, evolution of time would not change this initial state because the potential is time independent. However, classically we expect the electron to collide with the sphere. So, it seems that the quantum and classics predict different behaviours!

Similar threads

Replies
1
Views
1K
Replies
11
Views
2K
Replies
21
Views
2K
Replies
4
Views
3K
Replies
4
Views
933
Replies
5
Views
1K
Back
Top