H2O Vibrational Transitions (molecular as opposed to election) Why ?

  • Thread starter karen_lorr
  • Start date
In summary, the color of water is due to the energy levels and gaps between them in the hydrogen bonds, resulting in selective absorption and reflection of certain frequencies of light. This is different from other materials due to the specific configuration of the molecules and their associated energy levels.
  • #1
karen_lorr
63
0
Good morning.

Yet another question ;-)

I have been looking at so many websites and I still can’t find the answer, so if anyone could give me a simple explanation, or give a link to a web page, it would be really appreciated.

Visible wavelength selective absorption/reflection.

Water is blue as the H2 selectively absorb/emit various frequencies at the lower end of the visible spectrum. But in everything else is at a MUCH smaller scale (of the electron).

I understand how electron frequencies selectively absorb / emit frequencies. But why is H2O different.

I have found many explanations of the results but none that explains the causes.

Why would virtually all other object’s electrons react to energy waves but the scale is much larger in water (where the hydrogen bonds contract, shake, expand, warp, etc) and make the H the “active” element in the absorption/emitting. (sorry can’t think of a better word than Active).

I would have thought that if other objects containing either H or O have the H or O’s electrons selectively absorb the energy then the same should be true of water. But it isn’t?

Why?

Is it the strength/relative length/configuration/etc of the hydrogen bond or something completely different?

Sorry to ask so many questions but I really am trying to understand what is the difference between water’s "colour" and virtually everything’s.

Thank you
 
Physics news on Phys.org
  • #2
It's the energy levels and gaps between them that determine the frequency of EM that is absorbed / emitted. Although we start off by looking at the Hydrogen atom in terms of the electron energy, it's really the energy of the proton-electron pair (both charges). In the case of molecules, there are charges distributed within the molecule and it is the energy associated with re-arranging these charges that determines the frequencies of EM that will interact with them. But, in a condensed medium like liquid water, all the electrons and protons in each molecule are influenced by the charges in the nearby molecules too. This results in interaction with spectral bands rather than with just lines. In the case of water, the longer wavelengths happen to be absorbed more than the short wavelengths so the light with a long path through pure water will look blueish (i.e. white minus the redish wavelengths)
 
  • #3
The energy levels of the water molecules electrons only absorb radiation in the UV range. The visible light absorption is mostly due to the vibrational modes between the 3 atoms.
http://en.wikipedia.org/wiki/Electromagnetic_absorption_by_water
http://en.wikipedia.org/wiki/Color_of_water#Intrinsic_color

Other materials do not have the same configuration as water, so their electrons may absorb energy in the visible range or not depending on the specific material.
 
  • #4
Drakkith said:
The energy levels of the water molecules electrons only absorb radiation in the UV range. The visible light absorption is mostly due to the vibrational modes between the 3 atoms.
http://en.wikipedia.org/wiki/Electromagnetic_absorption_by_water
http://en.wikipedia.org/wiki/Color_of_water#Intrinsic_color

Other materials do not have the same configuration as water, so their electrons may absorb energy in the visible range or not depending on the specific material.

Just referring to electrons is to miss out the important energy levels associated with the positive charges, too. That wiki link of yours, about vibrational modes, makes it clear that it is the nuclei as well as the electrons that are involved.
 
  • #5
Than you all for your time and knowledge.

I "think" I have it now.

Due to "vibration" of the H2O being at the same frequency of some of the spectrum (many the shorter wavelengths - greens, yellows, reds) it is those that are absorebed.

But I stil don't understand why this would not be the case for anything with molecular movment - provideing it was within the frequency of any light hitting it.
What makes water different?

I understand that there will be multiple bonds - but isn't this the case with many "things"
 
  • #6
Yebbut the devil is in the detail. It's the actual energy level values that count and hydrogen bonds in water are 'just right'. Nothing wrong with coincidences, you know! There will be other transparent substances that 'just happen' to absorb Infra Red, no doubt.
 

What is the significance of H2O vibrational transitions in molecular science?

H2O vibrational transitions play a crucial role in understanding the behavior and properties of water molecules, which are essential for many chemical and biological processes. These transitions involve changes in the energy levels of the molecule, providing valuable information about its structure, bonding, and reactivity.

How do H2O vibrational transitions differ from electronic transitions?

H2O vibrational transitions involve changes in the vibrational energy levels of the molecule, while electronic transitions involve changes in the electronic energy levels. Vibrational transitions are typically associated with infrared light, while electronic transitions can occur in the visible or ultraviolet regions of the electromagnetic spectrum.

What factors influence the frequencies of H2O vibrational transitions?

The frequency of H2O vibrational transitions is determined by the masses of the atoms in the molecule, as well as the strength of the bonds between them. The type of vibration, such as stretching or bending, also affects the frequency. Additionally, the environment surrounding the molecule can impact its vibrational frequencies.

How are H2O vibrational transitions studied?

H2O vibrational transitions are typically studied using techniques such as infrared spectroscopy, which measures the absorption or emission of infrared light by the molecule. This provides a spectrum of the molecule's vibrational energy levels, allowing scientists to identify specific transitions and analyze their frequencies and intensities.

What applications do H2O vibrational transitions have in practical science?

H2O vibrational transitions have numerous applications in fields such as chemistry, materials science, and environmental science. They are used to study the behavior of water molecules in different environments, as well as to identify and characterize different types of molecules. Additionally, H2O vibrational transitions are used in the development of new materials and technologies, such as sensors and medical devices.

Similar threads

  • Other Physics Topics
Replies
16
Views
4K
  • Other Physics Topics
Replies
1
Views
1K
  • Other Physics Topics
Replies
5
Views
1K
  • Other Physics Topics
Replies
3
Views
2K
Replies
6
Views
767
Replies
2
Views
967
Replies
1
Views
775
Replies
18
Views
1K
Replies
6
Views
1K
Replies
8
Views
1K
Back
Top