Will CO2 absorb photon in all directions?

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Robittybob1

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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. :)
 
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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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

Q. What kinds of radiation pass through the atmosphere, and what kinds are absorbed?

A. Visible radiation ranges from about 0.35 to about 0.75 micrometers in wavelength. Very little visible radiation is absorbed by gases in the atmosphere. About 30-31 percent of incoming solar radiation is reflected and about 19 percent more is absorbed, mostly by clouds and particulate matter rather than by carbon dioxide and water vapor and oxygen. Those gases absorb a small amount of visible light, but not much. This is in contrast to the infrared (wavelengths greater than about 0.75 micrometer) radiation emitted by the earth's surface. This radiation has wavelengths mostly between about 2 and 20 micrometers and over 90% of it is absorbed by water vapor, carbon dioxide, methane, ozone, nitrous oxide, fluorocarbons, and other radiatively active ("greenhouse") gases on the way up.

Radiatively active gases are active in specific wavelengths of radiation. For example, if we could see in the infrared spectrum between 5 and 8 micrometers, we could not see the earth's surface (even on a clear day) from an aircraft at 10 km altitude. This is because water vapor is "opaque" in those wavelengths, and there is water vapor in the atmosphere even when there are no clouds. On the other hand, on a clear day, you can see snow-capped mountains pretty clearly at distances of over 100 km, because water vapor is transparent in the visible wavelengths. Admittedly, at large distances (e.g., about 100 km), things usually get pretty hazy because of light scattering by particulate matter and other aerosols in the atmosphere, which increase with line-of-sight distance. However, this reduction in visibility is not due to absorption by atmospheric gases. Because "seeing" in the infrared is not a part of most people's everyday experience (unless they work for the border patrol or as a bombardier), it is a little difficult to come up with "everyday" examples of what things would be like, for comparison with "everyday" visibility.

Probably the best example from "everyday" experience in the visible range, at least for those of us who fly a lot, is to notice that the moon is not any brighter when you're flying above 80% of the atmosphere than it is at the ground on a clear night. (Checking this by looking at the sun is NOT recommended, you can injure your retina pretty badly that way). If you live near the mountains, you can vary your elevation without having to fly. Also, a temperature map of the United States reveals that surface temperature is more related to latitude and distances from the coast than to elevation; the amount of solar radiation available to warm the earth's surface is about the same at high elevations as it is near sea level. In fact, at a given latitude it's often colder at higher elevations (one would expect it to be warmer if higher elevations get more solar radiation), but this is due to factors other than solar radiation.

Solar radiation" and "visible light" are not exactly the same thing. Solar radiation contains some wavelengths less than 0.35 micrometers, and some longer than 0.75 micrometers. Fortunately for us and other living things, most of the ultraviolet radiation (wavelengths shorter than visible) from the sun is picked off in the high atmosphere. This highly energetic radiation can strip electrons from atoms, causing the ionosphere and its associated phenomena such as aurora and the variations in your radio's ability to pick up distant broadcasting stations. Ozone in the middle and high stratosphere also picks off a lot of ultraviolet radiation, thereby preventing it from reaching the surface and causing skin cancers. The atmosphere's ability to absorb radiation drops off sharply between about 0.3 micrometers (near-visible ultraviolet) and 0.4 micrometers (visible blue-violet). Thus, we are protected from the harmful ultraviolet radiation, but still can see clearly for large distances. This differentiation is not always made in meteorology textbooks, so students sometimes come away thinking that the small percentage of "solar radiation" absorbed by the atmosphere is a part of the visible spectrum; instead, a lot of it is in the ultraviolet. [TJB]
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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.:)
 
prometheus said:
Waiting an average of 15 minutes between posts is hardly patient...
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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! :)
 
Robittybob1 said:
Will CO2 absorb photon in all directions?
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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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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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1. the energy of a photon
From Yahoo Answers there was a formula and an example given.
E=hv
h = planck constant
v = "nu" = frequency = c/(wavelength)
c = speed of light = 300x10^6 m/s

h = 663x10^-36 J s

so for wavelength = 300 nm ->
E = h * 300x10^6/(300x10^-9) = 663x10^-21 J
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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.
 
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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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The largest green house gas is water.

The 13 million million tons of water in the atmosphere (~0.33% by weight) is responsible for about 70% of all atmospheric absorption of radiation, mainly in the infrared region where water shows strong absorption.

Water contributes significantly to the greenhouse effect ensuring a warm habitable planet, but also operates a negative feedback effect, due to cloud formation reflecting the sunlight away, to attenuate global warming.
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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.

shade_38.jpg


watopt.gif
 
wellwisher said:
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.

http://www.gothicarchgreenhouses.com/images/shade_38.jpg

http://www.lsbu.ac.uk/water/images/watopt.gif
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How come your URLs were missing? I want to know what is being measured.
Absorption coefficient - What is that?
 
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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. :)
 
wellwisher said:
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.
Click to expand...


Hi wellwisher, Robbitybob1, everyone. :)

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! :)

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

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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. :)
 
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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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?
 
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