What are vibrational levels and energy states?

In summary, UV-Vis spectroscopy is based on the principle of electrons jumping to higher energy states. Each energy state contains multiple vibrational energy levels. The ground state is the initial state of all electrons before excitation and has approximately 20 vibrational energy levels. At room temperature, the probability of finding a molecule in an excited vibrational state is very low, so step one typically occurs from the ground vibrational state of the ground electronic state. However, in reality, de-excitation by photon emission can result in the molecule being in an excited vibrational level.
  • #1
CrimpJiggler
149
1
I know that UV-Vis spectroscopy is based on the principle of electrons jumping to higher energy states but I just read that each energy state has a number of "vibrational energy levels" inside it. Heres a diagram:
photlum1.gif

I'm confused now, what is a vibrational energy level and what is an energy state? The ground state is the state that all electrons are in before excitation and according to that diagram, the ground state has around 20 vibrational energy levels in it. Why would electrons in the ground state molecule be in any of those higher vibrational energy levels, as opposed to being in the lowest vibrational energy level?
 
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  • #2
The black lines are vibrational energy levels and the different electronic states are represented as the three "columns."

At room temperature, the probability of finding a molecule in an excited vibrational state is generally very close to zero, which is why step one is seen as only taking place from the ground vibrational state of the ground electronic state. I would however quibble about the fact that arrows 2 and 3 only points towards the ground vibrational state. In reality, most of the time de-excitation by photon emission will result in the molecule being in an excited vibrational level.
 

1. What are vibrational levels and energy states?

Vibrational levels and energy states refer to the different energy levels that molecules can exist in. These levels correspond to the different vibrational motions of the atoms within a molecule. This concept is important in understanding the behavior and properties of molecules.

2. How do vibrational levels and energy states affect molecular properties?

Vibrational levels and energy states play a crucial role in determining the physical and chemical properties of molecules. The energy states determine the stability, reactivity, and spectroscopic behavior of molecules, while the vibrational levels affect parameters such as bond lengths, angles, and dipole moments.

3. How are vibrational levels and energy states quantized?

Vibrational levels and energy states are quantized because they can only have discrete values, rather than a continuous range of values. This is due to the fact that the energy of a molecule is directly related to its vibrational frequency, which can only take on certain values according to the laws of quantum mechanics.

4. What is the relationship between vibrational levels and energy states?

The relationship between vibrational levels and energy states is that as the energy of a molecule increases, its vibrational levels also increase. This means that a molecule in a higher energy state will have more vibrational levels available to it than a molecule in a lower energy state. Additionally, the energy difference between two vibrational levels is equal to the energy of a photon with a frequency corresponding to the difference in energy between the levels.

5. How do scientists study vibrational levels and energy states?

Scientists use a variety of experimental techniques, such as spectroscopy, to study vibrational levels and energy states. Spectroscopic methods involve measuring the absorption or emission of light at different wavelengths, which can provide information about the energy levels and vibrational motions of molecules. Theoretical calculations, such as ab initio or density functional theory, can also be used to predict and study vibrational levels and energy states.

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