What does propogation of wave packets mean?

In summary, the article discusses the photo induced ligand loss of metal carbonyl complexes and how early semiempirical calculations have led to more advanced ab initio methods that can model the electronic structure and wavepacket propagation on potential energy surfaces of optically accessible excited states. The conversation then focuses on understanding wavepackets and their role in this process, with an explanation of wave functions and their collapse upon observation. There is some confusion about the concept of wavepackets and whether they refer to a sum of wave functions or waves of something else.
  • #1
mycotheology
89
0
I'm reading an article about the photo induced ligand loss of metal carbonyl complexes at the moment and here's a bit I'm having trouble getting my head around:
Early semiempirical calculations laid the foundations for subsequent ab initio
methods which can now not only describe the electronic structure of optically
accessible excited states, but also model the wavepacket propagation on the resulting
potential energy surfaces.

Its the wavepacket part that I'm confused about. All I know is that a wavepacket is what you get when you combine multiple sine waves. I have no idea how this applies to an actual compound. Can anyone explain it in practical terms? When you shine light on the compound, the carbonyl ligands jump to higher energy states, similar to how electrons do. Where do wavepackets come into it?
 
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  • #2
I am only an undergrad, so if someone more knowledgeable than me wants to illuminate us (or just me if I'm incorrect), I appreciate it.

My QM book discusses wave packets a little in the first few chapters. In QM, the particles you study are actually waves (not just point particles). Wave functions exist in a space (mathematically) such that they can be described as the sum of a bunch of different wave functions. These waves have probabilities of giving specific values when observed and the act of observation "collapses" the wave function such that subsequent measurements will yield the same result. On wave packets, my book more or less says: "A particle's velocity is not the speed of the individual ripples (phase velocity) but the speed of the 'wave packet' (group velocity)." I'm assuming, the wave packet refers to the sum of all of the wave functions that correspond to a "velocity measurement".
 
  • #3
Dead Metheny said:
On wave packets, my book more or less says: "A particle's velocity is not the speed of the individual ripples (phase velocity) but the speed of the 'wave packet' (group velocity)." I'm assuming, the wave packet refers to the sum of all of the wave functions that correspond to a "velocity measurement".

I'm not sure if this assumption is correct. Any quantum system has only one wave function. The wave function describes all possible configurations of the system. So a wave packet should not be a packet of wave functions, but a packet of waves of something else: for example electromagnetic waves. But correct me if I'm wrong.
 

1. What is a wave packet?

A wave packet is a localized disturbance or oscillation that travels through a medium, carrying energy and momentum. It is a combination of multiple waves with different frequencies and wavelengths, and has a finite size and duration.

2. How does a wave packet propagate?

A wave packet propagates by moving through the medium and transferring energy and momentum. The individual waves within the packet interfere with each other, causing the packet to spread out as it travels.

3. What factors affect the propagation of wave packets?

The propagation of wave packets is affected by the properties of the medium, such as its density and elasticity, as well as the frequency and amplitude of the waves within the packet. The shape and size of the packet also play a role in its propagation.

4. Why is the propagation of wave packets important?

The propagation of wave packets is important in understanding many natural phenomena, such as sound and light propagation, as well as in various applications such as telecommunications and signal processing.

5. Can wave packets propagate in a vacuum?

No, wave packets cannot propagate in a vacuum as they require a medium to transfer energy and momentum. In a vacuum, there is no medium for the waves to travel through and thus the packet cannot propagate.

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