Will CO2 absorb photon in all directions?

Discussion in 'Physics & Math' started by Robittybob1, Mar 16, 2012.

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  1. Robittybob1 Banned Banned

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    Will CO2 absorb photon in all directions?

    Let's look at the situation of the greenhouse gas CO2 and the wavelength of Infra Red light (IR) that it takes up.
    From that wavelength we should be able to work out the energy that is transferred to the molecule.
    Is there a velocity of the CO2 if it is contrary to the direction of the energy in the photon that will preclude absorption, the reason being that there is no way the two can interact and result in conservation of momentum and conservation of energy?
    These are the issues will be explored to find the science and maths needed to understand what scientific principles have to be considered.

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  3. Robittybob1 Banned Banned

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    Equations needed are:
    1. the energy of a photon,
    2. momentum of a photon.
    3. Kinetic energy equation (for molecules).
    Facts that are needed will be:
    1. mass of the molecule of CO2 and its components.
    2. Bond strengths between C-O in the carbon dioxide.
    3. Wavelengths of the IR absorbed by CO2
    we will add to this list as we go.

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    Last edited: Mar 16, 2012
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  5. Robittybob1 Banned Banned

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    This website is designed to inform people of the Greenhouse Gas issues. I have copied on small section that seems to give a broad coverage of the information regarding the Earth's atmosphere:

    Carbon Dioxide Information Analysis Center
    Frequently Asked Global Change Questions

    http://cdiac.ornl.gov/pns/faq.html

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  7. Robittybob1 Banned Banned

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    I thought someone might have provided some of the answers. Looks like I'm going to have to do it myself. So I hope no one complains that all the posts so far are mine, but I've been waiting for someone to join in.

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  8. prometheus viva voce! Moderator

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    Waiting an average of 15 minutes between posts is hardly patient...
     
  9. Robittybob1 Banned Banned

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    The first few were to set up the thread and then I waited 12 hours for a response. I am wondering what I will have to do to make the thread interesting. I was hoping a joint approach was the way, but so far it hasn't worked.
    Maybe everyone will just sit back and see if I can do the maths!

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  10. Robittybob1 Banned Banned

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    In the normal day to day situation light travels from the Sun and some is absorbed by the Earth and heats up as we all know. The heated ground radiates infrared radiation (IR) in all directions, and all around in the atmosphere are CO2 molecules moving in every conceivable direction. Even if it is impossible to tell what specific alignment is optimum for the IR to be absorbed, one cannot tell, for all we can see is the certain frequencies are absorbed and others aren't.
    There is a good graph of this here in the article headed "Greenhouse Gases Absorb Infrared Radiation"
    http://www.elmhurst.edu/~chm/vchembook/globalwarmA5.html (for the complete article)
    http://www.elmhurst.edu/~chm/vchembook/images/irCO2.JPEG
    From there we can see two portions of the spectrum are absorbed. (With varying transmittance [author is still to find out what that means].)

    Now it easy to think that if this absorption is to occur the right alignment between IR and the CO2 molecule need to be present, and the problem is overcome by the numbers of rays and molecules combined.
    And this is possibly part of the reason the more CO2 in the atmosphere there is, the more heating (absorption) can occur. Up to the limit of the number of Infrared rays (once all the band is absorbed more CO2 gas is not going to make any (or as much) difference for ultimately it was the energy in the IR that contributes to the increase in the kinetic energy (measured by temperature increase) of the atmosphere.

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    Last edited: Mar 17, 2012
  11. Robittybob1 Banned Banned

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    From http://www.elmhurst.edu/~chm/vchembook/images/irCO2.JPEG you can see there are two types of vibration induced by the absorption of IR.
    They are called "bond stretching" and "bond bending".
    Now from the physics needed to get these effects with "single hit" IR package of momentum, I propose that bond stretching is the IR photon interacting with the Oxygen portions of CO2 and there being 2 Oxygen atoms this is a more common interaction than one affecting the Carbon.

    Bond bending on the other hand can be induced by an energetic punch to the central Carbon atom.
    Now these suggestions are just from my practical knowledge and prior observations of larger systems. You can easily prove these yourself. You could attach 3 balls together with springs and see how you could induce these two distinct types of vibration.

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    Last edited: Mar 17, 2012
  12. Robittybob1 Banned Banned

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    1. the energy of a photon
    From Yahoo Answers there was a formula and an example given.
    Well we won't have any trouble once we know the frequency or the wavelength of the IR being absorbed by the CO2.
    It is also interesting to note the photon absorbed is also able to be re-radiated at the same frequency.

    So the right frequency set up the one of two addition movements in the CO2 molecule. Either bond stretching or bond flexing occurs, but from what I understand these are a all or nothing state. The flexing is done at a certain frequency, there is no half rate flexes, for if that was the case all frequencies of IR would be absorbed from the beginning.
     
    Last edited: Mar 17, 2012
  13. RealityCheck Banned Banned

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    Hi Robbitybob1. Just came in for a minute to check something and saw your thread.

    Can't stay, so briefly....

    Statistically speaking, the more CO2 then the larger the gaseous CO2 atmospheric layer cross-section the IR has to go through. And since in any large layer of CO2 there would be a high probability that at least one CO2 would be going in just the right direction (during its short mean free flight distance), then the IR is bound to be more likely to be absorbed when the numbers of CO2 are greater.

    The other aspect is that the more CO2 there is the more it will diffuse HIGHER into the upper layers of the atmosphere because of the concentrations (CO2 component partial pressure) in the lower layers increasing.

    When that becomes a serious part of the absorbing 'CO2 blanket', then even the IR radiated by high water vapour/clouds will be trapped when it wasn't before. So te 'blanket' will begin to trap/absorb IR that previously may have escaped before because it wasn't radiated from lower down.

    Rushed. Gotta go. I hope you got my drift? Cheers.

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  14. wellwisher Banned Banned

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    The largest green house gas is water.

    As the earth heats up and more water is within the atmosphere there are also more clouds reflecting the sun light so the heater for the greenhouse is less effective. This is why, even with humans giving it their best shot for a century, we only got about 1 degree. The water is not helping the cause.

    As an analogy, say we had a greenhouse in the summer. We might cover it with a white cloth to reflect the sun. Even of we add extra CO2 in the greenhouse the shade cloth won't allow the temperature to rise as much as expected, if we did not have this negative feedback by the farmer.

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  15. Robittybob1 Banned Banned

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    How come your URLs were missing? I want to know what is being measured.
    Absorption coefficient - What is that?
     
    Last edited: Mar 18, 2012
  16. Robittybob1 Banned Banned

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    It might be true that water H2O is a greater Greenhouse Gas (GHG) than CO2 but i want to specifically look at CO2 as it is the dominant gas on the atmosphere of Mars and Venus. Once we get the principles that apply we will look to see if they can be taken across the other types of GHGs.

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  17. RealityCheck Banned Banned

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    Hi wellwisher, Robbitybob1, everyone.

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    Regarding WATER clouds, the effects of these will be two-way because, while they reflect certain visible solar radiation, they will absorb IR solar radiation; moreover, while they do this for INcoming radiation, they will also at the same time be absorbing/reflecting radiation coming UP directly from the ground falling beneath them AND ALSO to/from the ground well beyond their edges which is scattered towards/from the cloud cover from the side.

    CO2 (and methane etc GHGs allow most solar radiation through and stop nearly all the IR from the ground ALL OVER the globe (unlike the Water clouds which are only involved where they occur LOCALLY, which is often a small percentage of the overall global surface/atmosphere).

    That is why CO2 and methane etc are much more dangerous/effective/ubiquitous in their effects than cloud cover. Hence the danger from them is more ubiquitous and CONTINUOUSLY ACTING even at night when the sun is not shining (and clouds are not shielding us from some of the solar radiation while adding there own re-radiation downwards to the surface of what they have absorbed during the day....which is why cloudy nights are usually a little warmer than clear-sky nights).

    Anyhow, it's complex but one thing is clear, the CO@ and other non-water vapour gases are most active and persistent and ubiquitous, so we can discount water clouds because the CO2 et al effects/contributions are what will more quickly buid up the heat and take us to the 'tipping point' where vast quantities of heretofore 'locked up' CO2 and Methane (in Chlathrates and peat and wetlands/ocean water etc) will then boost the Greenhouse Effect contribution to much greater levels than the current CO2 levels are making.

    So the danger is not what is happening NOW, but rather what will happen once the 'tipping point' is reached. And all this is happening over many magnitudes shorter 'geological periods' than in the past 'natural' cycles/events in climate change history/prehistotry.

    Sobering to consider. Cheers anyway....for humans will find a way (eventually) to survive it all even if we have to pay a sobering price for the lesson-learning on the way there!

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    Good luck and good thinking, everyone (we'll need both of these in large measure!

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  18. Robittybob1 Banned Banned

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    Things we need to know:
    2. momentum of a photon.

    "Momentum of photon before collision = h /wavelength"

    Now this site might give us the answer to that question when discussing the Compton effect. Now to understand the angles they are using it would pay to look at the webpage

    http://www.citycollegiate.com/comptons_effect.htm

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  19. Robittybob1 Banned Banned

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    3. Kinetic energy equation (for molecules).
    E = 1/2 mv^2 would be the usual kinetic energy calculation
    Mass (m) would be the mass of the CO2 molecule
    The velocity of the molecule would not be known ( the average kinetic energy of CO2 at that temperature could be used, but I will be looking at the increase in velocity rather than the absolute velocity if that is possible.

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  20. Robittybob1 Banned Banned

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    Facts that are needed will be:

    Facts that are needed will be:
    1. mass of the molecule of CO2 and its components.
    CO2 in kg = 7.31 * 10^-26
    O2 in kg = 5.326 * 10^-26
    carbon atom in kg = 1.994474834e-26

    2. Bond strengths between C-O in the carbon dioxide.

    C=O bond strength is 187 kcals/mol (2 x 93.5)

    3. Wavelengths of the IR absorbed by CO2

    Mass of CO2 in Kg, mass of the component Carbon atom and the two oxygen atoms. (These masses may come into the analysis of the vibrations.)

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    Last edited: Mar 18, 2012
  21. Robittybob1 Banned Banned

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    Now to really define the energy levels of the IR that CO2 absorbs.

    Any help welcome to discover this.

    The article "Infrared Spectroscopy" is very informative. http://www.wag.caltech.edu/home/jang/genchem/infrared.htm

    It uses 2 frequencies of absorption for CO2 "except where the sample absorbs: at 2349 (4.26 um) and at 667 (15.00 um). "
     
    Last edited: Mar 18, 2012
  22. Robittybob1 Banned Banned

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    Getting closer to applying maths to the situation! Any starters?
     
  23. Robittybob1 Banned Banned

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    First attempt: to see how much addition velocity a molecule of CO2 would have after absorbing IR photon.

    frequency 2349 Hertz, Plank's constant 6.63E-34 kgm^2/sec, Energy 1.56E-30 J, mass 7.31E-26 kg Velocity 0.00652568 Meters/sec.
    frequency 667 Hertz, Plank's constant 6.63E-34 kgm^2/sec Energy 4.42E-31 J, mass 7.31E-26 kg Velocity 0.00347734 Meters/sec.


    So that seems a surprisingly small rate increase considering molecules are moving at 100s of meters per second in room temperature air.
    and after a IR ray is absorbed by it it only rises by as little as between 3 - 7/1000 ths of a meter/sec?
     
    Last edited: Mar 19, 2012
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