Will CO2 absorb photon in all directions?

Billy T,

I pose the question again. Perhaps my confussion was not clearly stated. It seems that both carbon and oxygen interact independently in the near IR and at times IR range of the spectrum. While it is certain that where these atoms are associated with a molecule, any independent interaction must affect the whole molecule. It is also the case the the range within the spectrum that both oxygen and carbon interact with photons is modified by their association with any particular molecule, and is affected by different molecular associations.

Are you saying that an IR photon is not absorbed and or emitted by "an" electron, when that electron is part of a CO2 molecule? This does not seem consistent with experience.

Robittybob1, began this discussion examining IR interaction only, but both the CO2 molecule and its constituent atoms interact with light — photons, over a wider range of the spectrum, than just the IR portion and that interaction is modified by a number of "other" factors.

My question was, are you saying that IR photons do not interact with individule electrons within the CO2 molecule? Understanding that any interaction of any photon with any electron in an atom or molecule does has an impact on the whole.

 

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My point was that the size of a photon's wavelength and the size of an atom do not seem to have any relationship to whether they interact. In your earlier post you introduced what sounded as though the sizes were involved.

It has and remains my understanding that photons interact with the electrons, of an atom.., and in some cases as with gamma rays, at times with the nuclear components. How and when that interaction occurs is most certainly affected and to some extent determined by molecular composition and perhaps environment, but the interaction remains an interaction with the charged particles, rather than the atom or molecule as a whole.

This is where I was confused by your earlier post.

BTW providing a link to a reference that is not generally available, in a discussion with individuals who often have no access, is no better than saying, "Because I said so!". Mentioning a book as reference is O.K. But links should be accessible to the public.

 

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If the EM wave energy is reduced in discrete steps, i.e. a photon is absorbed, then there is little importance to the wavelength to absorber size ratio.

If, however, the EM wavelength is too long to be usefully considered to be a large nunber of photons then there is great significance to this size ratio - take anntena design for radio (or even TV and microwaves) as case in point.

The problem of photon, how they individually take different paths in interferometers yet always are locally abosorbed, is not within the realm of human understanding which is experience based - only can be mathematically described to predict what can be observed in their interactions with mater. (EACH photon passes thru every possible path of the interferometer as it only interferes with itsself when back at the detector. - This can be proven with such low intensity light source that normally no photon exist and never two at same time yet the photographic film after hours of exposure will show the same intervference pattern as if the exposure were only for one second with a brighter source!) No way a human can understand that!

Google search on:"Photons interfer only with themselves experiments" - I don´t know why I am only getting books as hits. I can not copy (seems to be a .pdf file) them but can read. What I copied and posted was the google hit text before opening the hit link, just to be able to qoute it.

Yes that is correct IF speaking of one photon being absorbed. It will excite to higher level or eject (usually) only one electron directly. However if speaking of EM wave, say sunlight, then its interaction with mater is more properly understood (at least classically) as the EM waves´s E field accererates many bound electrons but continues to exist. These accelerated electorns radiate EM waves at the same "driven frequency." Thus the total EM wave is the sum of the driving wave and the induced radiation, which has a 90 degree phase shift (as I recall) This "sum wave" proceeds thru transparent material at less than the vacuum speed of light, and the effect is wavelength dependent. (More effect when frequency is near to natural resonances of the bound electrons. - why refraction exists and why prisims spread out the solar sprectrum.)

Not wanting to simply assert facts, I did do quick Google search and gave two of the result as links with brief quotes of text found there. The book link was interesting and I skimmed 40 or so pages, but it assumes you know some quantum physics. I don´t know why you can not do the same.

PS I just clicked on my link again as test. It opened on page 7, and I quickly as it would load went down to page 102. Perhaps you must do Google search and then click on resultant hit? I am not sure, but think I searched for "size of molecules in angstroms" Try that.

 

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This sounds a lot better. Perhaps it was just a knee jerk reaction on my part earlier.

This moves way outside of accepted mainstream views, but...

I have often wondered about the wave nature you describe and the possibility that the quantum expression of EM radiation as discrete photons might be an artifact of the fact that all of our means of measurement and observation, depend on atomic and molecular interactions with those waves, which seem to be clearly defined in a quantifiable manner.

I.e. If light or any EM wave interacts in a quantifiable way with matter, there will always be a quantifiable character to how we interpret many interactions between the two. We are in this respect, perhaps fish in a fish bowl...

Anyway, wether my earlier reaction was of my own interpretation or not, this last post was helpful in understanding your intent.

As for the Google book reference I just got a message saying I had exceeded my free access, though I had seen not even one page... Who knows...?

Thanks for your response.

 

The discussion has gone a little too wide. I wanted to examine the two IR wavelengths that are absorbed by CO2 and try and understand how it sets up these vibrations in the molecule. I proposed that as usual the electron and the photon interact. There is not sufficient energy to lift the electron to another orbital but in the process of stretching the orbital the momentum is absorbed by the whole CO2 molecule in a vibratory motion. From the reading there were the two types of vibration stretching and bending. This results in a net momentum change of the CO2 molecule (but the velocity increase was in the order of 10^-14 m/sec. This is an incredibly small change in velocity, but is transferred to other atoms depending on the collisions it is involved in.
So the average rate of velocity of the molecules goes up, i.e. the atmosphere heats up.
But because the photon induces a momentum change in the CO2 it has to be able to conserve that momentum. An interaction is not completed unless the photon can transfer the momentum. This means that in most cases the photon momentum and the CO2 had to be have a similar momentum vector. Meaning traveling more or less in the same direction.
If this is correct the absorption causes an increased motion in one direction in the case of atmospheric absorption (as the incident light is from one direction). As apposed to global warming after the photon has radiated from the ground surface, in which case it will be more random.

 

Whether you look at the IR radiation as photons or as a wave(s), I am unsure you can reduce the interaction to the kind of momentum transfer you are describing. The vibration of a CO2 molecule would seem to be almost at rest when compared to the velocity of light. And the velocity of light is the largest contributor to the rate at which the interaction takes place.

I tend to think that Billy T was perhaps correct in his assertion that in this case one should consider the IR radiation in the interaction, as a wave rather than as an individual photon or group of photons. Though I am still working on putting this all together in my own mind...

 

The reason we can make some of the assumptions is based on scientific knowledge.1. Photon electron absorption
2. Conservation of momentum
3. Observation of the winds around the planets. Strong prograde winds exist on planets where the sunlight can't hit the solid ground and patchy winds where it can.

There has to be some mechanism that makes the winds of Venus and Jupiter circulate the planets faster than the planets spin.
What is it? I have proposed it is via this unidirectional absorption of photons and it has been "proven" using valid scientific analysis.

Now we want to set up an experiment to see if we can mimic this effect.

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So are you thinking the molecule starts resonating at the photon frequency (bobbing up and down as the photon goes past it). I can see that happening in the ocean but what examples have we got WRT photons?

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What my intent was is to say that there is some merit to thinking of the IR radiation as a wave rather than strictly as photons in this case. Obviously light interacts with atoms, molecules and particles in a discrete quantifiable way. However, light or EM radiation also appears often to be a wave. This is especially apparent in the longer wavelengths as Billy T pointed out.

I think what I am saying is that it may be a mistake to restrict how we think of and treat EM radiation as either just photons or just waves.

As a photon or particle, it would semm that the interaction would take place over a time frame in which the kinetic vibration of a molecule would have no significance.

As far as emission and absorption being affected by the "angle" or direction of interaction, I am unsure it can have any impact. This returns to a previous statement that as a photon interacting with an electron, it is the energy match that is important and for that the kinetic vibration of an atom as a whole has little impact on the electron's energy state, where the direction of vibration during the interaction is the only issue.

 

Light or photons traveling in vacuum travel at "C". In water light travels slower than "C" so it might be able to show the reason light is slowed, and I would guess it because the photon is going to interfere with more electrons. So the point I'm making is that electron interaction creates a slight delaying effect. (Does the photon stop for a moment?) Same in the case of a gas the light passing through could be slowed.

 

For neutral atom or molecule the numbr of + charges (protons) is the same as the number of - charges (electrons) and if EM wave is large, all are in the same E -field so net force on that mater is zero. Molecule as whole, its center of mass, is not "bobbing up and down." Again stop inventing things to believe, read and learn what is fact. Think a little on this lack of center of mass movement with passing EM wave in IR range and read up on Coreollis effect to understand why average winds have a direction (Out of west in the US, etc.)

 

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Hi Rbb1.

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Bear in mind that depending on the mean free path velcities, collision accelerations, angles/attitudes of CO2-to-incoming-photon etc etc will give a range of possibilities fro REFLECTION, TRANSMISSION and ABSORPTION from/through/by the CO2 gas distributions/thicknesses/densities at various altitudes/temperatures etc.

Looking only at the 'absorption' rate/effect must be done in the context of the probability distribution for all th possible 'events' and the likelihood that any one photon will be iether reflected back down to earth, or transmitted through to space or actually be absorbed.

The 'modeling' for all this should be available in the scientific literature on such matters. I haven't looked for such, but it may be worth your while to at least see if some of your questions can be answered by such models?

Good luck! Cheers.

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I'm not making anything up, I was just trying to understand how you might be thinking so I was asking you. We know these photons make these CO2 molecules vibrate, so how do you think the photon achieves that?
If the net force is zero how does it make it move? This is your chance to explain how it might work.

I understand the coreolis effect but this does not play such a noticeable affect on Venus or Jupiter.

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Good suggestion. Did you know unless you have weeks of spare time these searches are out of the question.

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I am having a little difficulty visualizing what you are suggesting above. Do you mean to be suggesting that where the +/- charges of an atom are balanced all of the electrons exist as a single electron field?

Even then a EM wave could potentially interact with the field in an absorption/emission, or reflection event. It is not like the EM wave, whether it is a wave or a photon has a variable energy potential based on what it encounters. I have seen no reference to photon/electron interaction that suggests a variable energy level for any specific wavelength of light, though an atom's or electron's potential reaction or interaction range can change, as we discussed earlier.

As for the "bobbing up and down" bit you could probably read that as the kinetic interacting associated with heat. Atoms jiggles around at different rates depending on the heat involved.

 

These CO2 molecules vibrate (was that jiggling?) but as BillyT wrongly or rightly said around a non moving centre of mass. I sort of agree but the molecule will also be traveling through space at an average speed depending on the gas temperature and the wind speed can be added to that average as well.

But what I experience is that to get vibration into the molecule it has to be "bumped" in the right way. (Test: Make 3 objects connected with springs vibrate)
That initial bumping will be equivalent to the momentum of the photon, so not only is there energy contained in the vibration but there is a net momentum as well.
The net momentum will have the same vector of momentum (direction) as the IR photon. (The net momentum must be conserved.)

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Or was your jiggling Brownian motion? (Atoms colliding causing change of directions.)

 

From this site the absorption of the photon was more like what BillyT describes (theoretically)
http://teaching.shu.ac.uk/hwb/chemistry/tutorials/molspec/irspec1.htm

Well it will be interesting if we can find if the frequency matches in the CO2 molecule.
So it was more a bobbing up and down effect! That certainly could account for the energy in the photon, for in my calculations there was vastly more energy in the photons than was accounted for by the small change in velocity associated with the momentum.

 

This lecture http://faculty.atu.edu/abhuiyan/Course/Chem 4414/Chapter 16.ppt#256,1,Chapter 16 An Introduction to Infrared Spectrometry
really is quite helpful to explain where the photon energy can be utilized in the bending and stretching of the molecular bonds.

They treat the molecule as if the bonds are tiny springs so they calculate the "force constant of the springs"
I put the vaues into an Excel sheet and got the answers

3.16E-18 for the stretching bond affected by the photon at the 2349 Hz

2.55E-19 for the bending bond affected by the photon at the 667 Hz

Now these figures have no real meaning to me as such, but that is what I got.

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But thinking it over at those photon frequencies molecular bending matches the "natural spring frequency " with the molecules as the weights on the end of these imaginary springs.

Has any one ever measured the actual frequency of these vibrations or is it a matter of course?

 

I must thank BillyT and Only Me to help me sort out this problem. For I could see that the momentum and the energy of the IR photon had to be conserved, but only a fraction of the motion was in the form of momentum. What was I going to do with the excess of energy and now it has been shown to intensify the vibration of the CO2 molecule.
Thanking both of you again.
Momentum retains the same direction vector but energy can transform to any sort of energetic motion.

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How does one resolve the conservation of both the momentum and energy in the same interaction. Something to look at on another thread.

 

I think I might have spoken too soon for now I have my doubts about the molecule having the ability of containing the photon's energy simply in the vibration.
Can someone help me with the various bits of maths please?

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