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Physicist Response Required regarding photon / electron interaction

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posted on Aug, 8 2009 @ 03:06 AM
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I've been pondering recently on how technologically advanced we've become from the perspective that we've succesfully managed to make use of our "knowledge" of physics to create all the wonderful "gadgets" that we now take for granted. Things like computers, dvd players, cell phones, lcd/plasma tv's, ipods, and the list goes on and on.

Now, many of the devices we commomly use are completely dependent on our being able to generate and manipulate magnetic fields and other devices are dependent on us being able to generate and manipulate light. Then I got to thinking that even though we've become expert at generating/manipulating magnetic fields, when you really get down to it, we have NO IDEA at all what magnetism really is at a fundamental level. We "think" we do and have all manner of mathematical constucts to effectively model the "effects" and "behaviour" of magnetic fields ... but deep down we're really clueless as to what it REALLY is.

The same goes goes for our ability to generate/manipulate light. We have created all kinds of devices to create light of one kind or another e.g. light bulbs and lasers but again when you dig down deep enough, more questions than answers are generated.

Perhaps it's just me and I haven't researched thoroughly enough or looked in the right places, which is why I decided to take the easy way out by posting this thread and hoping someone with a sufficiently deep background in physics could answer the following "head scratcher" question for me.

It's to do with the "mechanics" of energy transfer from a photon to an electron, folowed by the re-emission of another photon by the same electron.

Anyone not interested can stop reading at this point.


Still with me ? Ok, here we go ...


I fully understand the basics of energy absorption by a valence shell electron (e.g. by collision with a photon of sufficient energy) causing it to be raised to a higher energy level where it remains for a time until spontaneously it drops back to a lower energy level and in the process emitting a photon based on the energy difference between the 2 energy levels.
That may not be a 100% accurate description but good enough for me !

So what's my problem then ?

My problem is that the above simplistic explanation (on my part) appears to be only a small part of the entire picture but apparently is the standard textbook answer. I'm not sure why a more in depth and rigorous explanation is not given but from what i can see the simple textbook answer seems to be more than sufficient for everyone.
It's as if nobody seems to care past the point of being told "Yep, a photon hits an electron, the electron then jumps to a higher energy level, then eventually falls back releasing a photon in the process ... nothing more to be seen here, folks ... so move on !"

But as I mentioned, I'd like a much more complete picture of what really happens.

Lets start with the photon speeding along to it's inevitable interaction with the electron. Now the photon is a packet of energy travelling at light speed and one has to assume that it doesn't simply exist as a point source but has some property that is the equivalent of "length". In other words, the photon must have a start point, an end point, and something inbetween seperating these two points i.e it has "length" no matter how short this "length" value may be.

Now, this photon is approaching the target electron which quantum physics tells us should not be considered to be analogous to a billiard ball that has a definitive spatial location (position) as it orbits the nucleus, but rather should be considered to be smeared out along the entire orbital path as a "mathematical wave function" surrounding the nucleus with it's "probable" position at a given point in that orbit corresponding to the probability of finding it at that point compared to any other point.

Continued next post ...




posted on Aug, 8 2009 @ 03:08 AM
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Continued from previous post ...


So here's my 1st question:

How close does the photon need to approach the electron before energy can be transferred from the photon to the electron ? Obviously there MUST be some minimum distance otherwise NOTHING would happen.

My 2nd question:

Assuming the photon and electron are "close enough" (see question 1), how is the energy transfer started ? In other words, what "information" is passed between the photon and electron to trigger the transfer ?

My 3rd question
The photon MUST have a MINIMUM energy level for transfer to take place ... otherwise the photon & electron do not interact. So, how does the electron "interrogate" the approaching photon to determine if it contains the required minimum energy or whether to "ignore" the photon entirely ?

My 4th question
Does the photons entire energy get transferred IMMEDIATELY (i.e. no time elapses) to the electron and if not, how long does it take ? And remember, the photon is zipping past the electron at light speed as this energy transfer takes place.

My 5th question
If the energy transfer is NOT immediate, then does the photon "red shift" as it transfers it's energy to the electron ?

My 6th question
It's explained (and then glossed over) that due to the absorbed energy, the electron "jumps" to a higher energy level i.e. orbit.

Does the electron have to wait for the ENTIRE energy packet to have been transferred BEFORE it can make this "jump" ? Or does it start to "jump" the moment the photons energy begins to transfer ?

My 7th question
Is the "jump" from one level to the next level instantaneous i.e. NO time involved ?
If not, how long does it take to complete the jump ?

My 8th question
Quantum physics tells us that the electron HAS to be in one level or another and CANNOT exist inbetween these levels. If that's so, where exactly IS the electron during the minute period of time AFTER it's left it's starting level and BEFORE it reaches it's new level ?

My 9th question
When "jumping", does the electron have to COMPLETELY leave it's starting level before it can "appear" in the new level ? Or can some "part" of the electron exist momentarily in BOTH levels e.g. 25%/75% or 50%/50% or 10%/90% ?

My 10th question
When the electron "drops" to a lower level, what initiates or triggers the creation of the new photon ?

My 11th question
Does the photon get created
(a) before the electron leaves it's current level ?
(b) when the electron has left the higher level BUT not appeared yet in the lower level ?
(c) after the electron has appeared in the lower level ?

My 12th question
Once the new photon creation process is triggered (by the jump to a lower level), does the photon appear instantaneously COMPLETE or does it get "built" gradually over time ?

My 13th question
If the photon gets gradually "constructed" i.e. energy is transferred from the electron to the new photon over time, does that mean the photon gradually blue-shifts during construction as more and more energy is transferred to it from the electron ?

My 14th question
I'm asssuming that the photon is created external to the electron ... so once the electron "releases" some of it's stored energy, what/where is the "mechanism" that takes over and manipulates this energy and "builds" a new photon outside of the electron ?

My 15th question
Once completed, how is the direction that the photon will now travel away from the electron, determined ?


PHEWWWWWW .... lot's more questions ... but that will do for now !

Any scientific geniuses out there willing to take a stab at answering my "trivial" and "very easy" questions ?




posted on Aug, 8 2009 @ 05:53 AM
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I'm disappointed at the lack of response ... does this mean no one here on ATS has a clue ?



posted on Aug, 8 2009 @ 08:07 PM
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Instead of answering one by one, I'll give a general answer that I hope can indirectly answer all your questions. First, the photon is a particle whose path is predeterministic. This means, everything surrounding its origin of movement has an exact cause that can be traced back to with enough effort (this may exceed our current abilities). The electron is held in orbit by the electromagnetic force. The photon is the "force carrier" of the electromagnetic force.

So instead of the photon directly interacting with the electron, it interacts with the electromagnetic field holding it in place. An extra photon, requires a further distance to even out the amount of total energy. One less photon = drop in distance. Whether this is a photon becoming part of a wave and then becoming a forced out particle afterwards or a photon joining the movement of other photons is speculation at this point but photons are already in every atom atleast in some capacity. This is how the photon seemingly has a physical effect without actually having any mass. I think I answered your questions one by one anyway but I feel this is a complete explanation of the photo-electric effect which is what you are refering to.

[edit on 8-8-2009 by Eitimzevinten]



posted on Aug, 8 2009 @ 09:54 PM
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How close does the photon need to approach the electron before energy can be transferred from the photon to the electron ? Obviously there MUST be some minimum distance otherwise NOTHING would happen.


I don't understand why the 'obviously' part. How far does your finger need to be from the keyboard before you can type a letter? Maybe its the same for photon-matter interactions, a minumun distance is not a must. To be perfetly honest, I do think there is such minimun distance, and if we are right and such distance exists, it's probably governed by Strong or magnetic forces?


Assuming the photon and electron are "close enough" (see question 1), how is the energy transfer started ? In other words, what "information" is passed between the photon and electron to trigger the transfer ?


photons do not carry information, unless you want to call energy(frequency) information. This is pretty analogous to classical mechanics - when you are trying to push an abject on the ground, you don't pass information to the object, you either can move it, or you can't. (think static friction coefficient)



The photon MUST have a MINIMUM energy level for transfer to take place ... otherwise the photon & electron do not interact. So, how does the electron "interrogate" the approaching photon to determine if it contains the required minimum energy or whether to "ignore" the photon entirely ?

There is no interrogation. If the photon is unable to excite the electron, the no light is absorbed.


Does the photons entire energy get transferred IMMEDIATELY (i.e. no time elapses) to the electron and if not, how long does it take ? And remember, the photon is zipping past the electron at light speed as this energy transfer takes place.

I don't know the answer to this question, but I would assume that any delay in the transfer has nothing to do with the constant c.


If the energy transfer is NOT immediate, then does the photon "red shift" as it transfers it's energy to the electron ?




Does the electron have to wait for the ENTIRE energy packet to have been transferred BEFORE it can make this "jump" ? Or does it start to "jump" the moment the photons energy begins to transfer ?


I don't know of any delay of an electron jumping between energy leves, it should be instantaneous. However, in the case of photoelectric effect, there is a delay between the absorption of the photon and the emission of the electron which is approx 10^-9s. However, we cannot assume that this delay is due to an energy transfer delay which would imply that the packet(or commonly known as photon) has a well defined size(which is not true). The delay is usually attributed to background noise.


Is the "jump" from one level to the next level instantaneous i.e. NO time involved ?
If not, how long does it take to complete the jump ?

As I understand energy level jumps are instantaneous.



Quantum physics tells us that the electron HAS to be in one level or another and CANNOT exist inbetween these levels. If that's so, where exactly IS the electron during the minute period of time AFTER it's left it's starting level and BEFORE it reaches it's new level ?

If my previous answer is correct, there is no time interval between levels.



When "jumping", does the electron have to COMPLETELY leave it's starting level before it can "appear" in the new level ? Or can some "part" of the electron exist momentarily in BOTH levels e.g. 25%/75% or 50%/50% or 10%/90% ?


The electron doesn't leave by parts. I think it has been shown that electrons can in fact be at two places at the same time, but I doubt that's the case here.


When the electron "drops" to a lower level, what initiates or triggers the creation of the new photon ?

You just answered your own question - unless you are asking what initiates the energy drop of the electron? I know nothing of Quantum field theory.



Does the photon get created
(a) before the electron leaves it's current level ?
(b) when the electron has left the higher level BUT not appeared yet in the lower level ?
(c) after the electron has appeared in the lower level ?

(d) none of the above: At the instant when the electron dissapears from the previous level, and reapears on the lower level.



Once the new photon creation process is triggered (by the jump to a lower level), does the photon appear instantaneously COMPLETE or does it get "built" gradually over time ?

If the photon gets gradually "constructed" i.e. energy is transferred from the electron to the new photon over time, does that mean the photon gradually blue-shifts during construction as more and more energy is transferred to it from the electron ?

You can't build a photon over time, its either there, or not there.



I'm asssuming that the photon is created external to the electron ... so once the electron "releases" some of it's stored energy, what/where is the "mechanism" that takes over and manipulates this energy and "builds" a new photon outside of the electron ?

Electrons don't release energy little by little.



Once completed, how is the direction that the photon will now travel away from the electron, determined ?

The direction is random, unless the emission is not spontaneous. In stemulated emission, the photon released follows the same direction as the stimulating photon.



I'm disappointed at the lack of response ... does this mean no one here on ATS has a clue ?

I'm sure someone here does, hopefully a physicist (don't take my word on any of the answers cause I'm not, pretty much just recalling my physics 3 class :p). IMO you would have gotten more replies if you had only mentioned absorption, emission, and then asked your questions, but the first page killed it.

[edit on 8-8-2009 by daniel_g]



posted on Aug, 8 2009 @ 11:07 PM
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reply to post by daniel_g
 


Thanks so much for taking the time to try and shed some light on my questions ... much appreciated !
But truthfully, the entire process still seems to be hidden behind a veil of ignorance. We KNOW that a photon/electron interaction can take place but we're totally in the dark as to the mechanism(s) behind the entire process.





How close does the photon need to approach the electron before energy can be transferred from the photon to the electron ? Obviously there MUST be some minimum distance otherwise NOTHING would happen.


I don't understand why the 'obviously' part ?

I'm assuming (unless told otherwise) that for the photon & electron to interact, that they must be within a certain distance of each other. Logic suggests that if they're on opposite sides of the universe that they will NEVER interact ... so the closer they get, the greater the probability of interaction. Which therefore implies there MUST be a minimum distance where interaction is guaranteed.





Assuming the photon and electron are "close enough" (see question 1), how is the energy transfer started ? In other words, what "information" is passed between the photon and electron to trigger the transfer ?


photons do not carry information, unless you want to call energy(frequency) information

What I'm trying to say is that if we consider the photon and electron to be independent entities, and that at some point the photons energy DOES get transferred to the electron, I'm wondering how that "transfer yes" decision is arrived at just before the energy is transferred across.





The photon MUST have a MINIMUM energy level for transfer to take place ... otherwise the photon & electron do not interact. So, how does the electron "interrogate" the approaching photon to determine if it contains the required minimum energy or whether to "ignore" the photon entirely ?


There is no interrogation. If the photon is unable to excite the electron, the no light is absorbed.

Thats what I'm asking ... how is it determined that the photon carries sufficient energy to excite the electron ?





Is the "jump" from one level to the next level instantaneous i.e. NO time involved ?
If not, how long does it take to complete the jump ?


As I understand energy level jumps are instantaneous.

That's were I'm confused ... to me, "instantaneous" means with NO TIME INVOLVED. But a "jump" from one energy level to a different energy level which one presumes do NOT co-exist in the same spacial location, implies a "distance"(i.e. between levels) is involved which further implies that TIME also must be involved.





When the electron "drops" to a lower level, what initiates or triggers the creation of the new photon ?


You just answered your own question - unless you are asking what initiates the energy drop of the electron?.

Sorry for the confusion ... yes, I wanted to know what initiates the energy drop in the electron.





Does the photon get created
(a) before the electron leaves it's current level ?
(b) when the electron has left the higher level BUT not appeared yet in the lower level ?
(c) after the electron has appeared in the lower level ?


(d) none of the above: At the instant when the electron dissapears from the previous level, and reapears on the lower level.

So ... the electron INSTANTLY disappears from one level and INSTANTLY reappears on another level and in the meantime, a photon INSTANTLY is created !!
Hmmmm ... lots of "INSTANTLY" but no answers to HOW all this marvelous stuff happens.



posted on Aug, 9 2009 @ 02:47 AM
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I know what you want to hear, its something like "from the electron a flow of God123 particles flows to a given point and a new photon is slowly created. The God123 particles remove energy from the electron and the electromagnetic force of the nucleous pulls the electron back to a lower orbit"

But it simply cannot be done. The problem is these are Fundamental Interactions, as in they cannot be described in terms of other interactions. As predicted, and as measured, they happen spontaneously

yes, physics =



Sorry for the confusion ... yes, I wanted to know what initiates the energy drop in the electron.


Vacuum fluctuations - the very same phenomena that's gonna prevent the LHC from creating a deadly blackhole. Let's hope for the best they got this one right



posted on Aug, 9 2009 @ 03:09 AM
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reply to post by daniel_g
 


I think in a way you're right ... we may just have to accept the fact that there are some fundamental processes that no matter how much we would like indepth details of, we never will be able to dig down that deeply to obtain them.

Could almost say there's a form of "information" event horizon surrounding some process that shield them from complete examination and total understanding !



posted on Aug, 9 2009 @ 03:39 AM
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This fella here looks promising.

Personally I see no reason to find the radius of an electron. But I could be wrong.

I am currently reviewing electrodynamics with particular regard to generation of EMF, and as I move along the learning curve I may get to Mr. Kong's work, at which time I will critique it.



posted on Aug, 9 2009 @ 04:14 AM
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Its all EM. Any movement by either the electrons or protons are just as likely to cause an effect in the field like a photon. The photon reacts with the EM field. Any change in the EM field is going to be expressed by a photon and then an indirect change in the electrons orbit and what not.



posted on Aug, 9 2009 @ 11:25 AM
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To the best of my knowledge and as I understand it (I'm not a physicist)


Originally posted by tauristercus
How close does the photon need to approach the electron before energy can be transferred from the photon to the electron ? Obviously there MUST be some minimum distance otherwise NOTHING would happen.


It has to hit it directly.


Assuming the photon and electron are "close enough" (see question 1), how is the energy transfer started ? In other words, what "information" is passed between the photon and electron to trigger the transfer ?


If I understand the things I read correctly, the energy transfer is done by a simple "running into".


The photon MUST have a MINIMUM energy level for transfer to take place ... otherwise the photon & electron do not interact. So, how does the electron "interrogate" the approaching photon to determine if it contains the required minimum energy or whether to "ignore" the photon entirely ?


A "photon", by definition, is a certain amount of energy. Anything more or less isn't a photon.



Does the photons entire energy get transferred IMMEDIATELY (i.e. no time elapses) to the electron and if not, how long does it take ? And remember, the photon is zipping past the electron at light speed as this energy transfer takes place.


The electron is not exactly a particle.


If the energy transfer is NOT immediate, then does the photon "red shift" as it transfers it's energy to the electron ?


No. "Red shift" is a phenomenon of light in motion. It just smacks into and gets absorbed. Like a drop of water dropping into a puddle of water.


Does the electron have to wait for the ENTIRE energy packet to have been transferred BEFORE it can make this "jump" ? Or does it start to "jump" the moment the photons energy begins to transfer ?


It's instant and total, as others have said.


Is the "jump" from one level to the next level instantaneous i.e. NO time involved ?


Yes.



Quantum physics tells us that the electron HAS to be in one level or another and CANNOT exist inbetween these levels. If that's so, where exactly IS the electron during the minute period of time AFTER it's left it's starting level and BEFORE it reaches it's new level ?


It's all instant. No "time" involved.



When "jumping", does the electron have to COMPLETELY leave it's starting level before it can "appear" in the new level


It doesn't flow like an amoeba. It's instant.



When the electron "drops" to a lower level, what initiates or triggers the creation of the new photon ?


A variety of things, mainly involving changes in the energy level of the atom (for example, when an atom is no longer being excited by a series of photons hitting it.)



Does the photon get created

Simultaneously, as I understand it.



Once the new photon creation process is triggered (by the jump to a lower level), does the photon appear instantaneously COMPLETE or does it get "built" gradually over time ?


Instantaneously.



If the photon gets gradually "constructed" i.e. energy is transferred from the electron to the new photon over time, does that mean the photon gradually blue-shifts during construction as more and more energy is transferred to it from the electron ?


No. There's no "blue shifting" there. That's a phenomenon of light in a relativistic frame, not of photons.



I'm asssuming that the photon is created external to the electron


It isn't. The electron "spits out a photon and transfers to a lower level simultaneously.



Once completed, how is the direction that the photon will now travel away from the electron, determined ?


It'd be determined by the environment around the atom (other atoms, magnetic fields, etc.)

I won't swear these answers are complete and magnificent. This is simply what I understand from reading... and I don't have any degrees in the high level maths or in physics.



posted on Aug, 9 2009 @ 10:52 PM
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reply to post by tauristercus
 


I think everyone answered your question adequately (well considering each question would require many paragraphs, equations, and images for a really detailed explanation) so I will only add this one bit...

Yes electrons (not a particle mind you, simply a wave (or energy packet) ) can be in the same place at once, this is called Superposition and is well defined within modern Quantum Theory.



***NOTE: The Superposition Principle only applies to the electron, the Pauli Exclusion Principle shows it is not possible for any non-electron related particle(Fermions, where electrons are Leptons).



****Also I am no physicist, just offering what help I can.


[edit on 8/10/2009 by jkrog08]



posted on Jan, 1 2010 @ 04:04 PM
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When quantum mechanics states that an electron cannot exist between energy levels, do they mean permanently exist? In otherwords can an electron temporarily exist between levels? This would eliminate the instantaneous "jump". Can the electron actually spiral down to the lower energy level? If so, then you have a half wave dipole antenna around the nucleus of the atom sending out a pulse of electromagnetic energy. The photon particle would be the actual border of the pulse of EM energy. The pulse would go from E2 amplitude to E1 amplitude and would be described mathematically using the cosine function. The actual length of the photon would be it's period which would be the time required to spiral down to the lower energy level. One axis would produce a linear polarized wave while the other two axis would produce a circularly polarized EM wave. I'm a layperson so this is just a simple idea for a solution to part of your question.



posted on Jan, 1 2010 @ 05:29 PM
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Originally posted by jkrog08
Yes electrons (not a particle mind you, simply a wave (or energy packet) ) can be in the same place at once, this is called Superposition and is well defined within modern Quantum Theory.



***NOTE: The Superposition Principle only applies to the electron, the Pauli Exclusion Principle shows it is not possible for any non-electron related particle(Fermions, where electrons are Leptons).


Are you sure you're reading into superposition properly? I think you're doing so backwards. The superposition principle states that when there are multiple possible states, the resulting state will be their combination. This is like wave superposition, where the intersection of two waves will result in their summation.
Electrons do not violate the Pauli Exclusion Principle. They cannot occupy the same state simultaneously.



Originally posted by tauristercus
Thats what I'm asking ... how is it determined that the photon carries sufficient energy to excite the electron ?

It is determined by whether or not it carries enough energy to transition the electron from its current state to the next excited state. More literally, the energy of the photon is determined by it's frequency -- ex. radio, x-ray, gamma, red, blue... The electron cannot exist between states, so if there is insufficient energy the electron cannot and will not jump.


Now in response to some other things, a photon is created exactly as an electron moves down to the lower state. To do otherwise would violate conservation of energy. It's simply:
1) Electron + energy (incoming photon) ---> 2) Excited electron w/ energy ---> 3) Electron + Emitted energy



posted on Jan, 1 2010 @ 06:27 PM
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Originally posted by jkrog08
reply to post by tauristercus
 


I think everyone answered your question adequately (well considering each question would require many paragraphs, equations, and images for a really detailed explanation) ....


I agree there have been some interesting answers but reviewing them all, one is still left with the feeling that no definitive explanations are being presented. It's just as I stated in my opening post that even though we KNOW how to manipulate light, magnetism and electricity on a gross level ... we still have minimal idea of whats really happening at the the atomic level.

Johnmike stated the following:


It is determined by whether or not it carries enough energy to transition the electron from its current state to the next excited state. More literally, the energy of the photon is determined by it's frequency -- ex. radio, x-ray, gamma, red, blue... The electron cannot exist between states, so if there is insufficient energy the electron cannot and will not jump.

and in doing so, once again showed how something is taken for granted or "understood" as in "It is determined ..." and "the electron cannot and will not jump.".
But not a further bit of information as to WHY the above is so.

And as Eitimzevinten says:


The photon reacts with the EM field.

But HOW exactly does the photon interact with the EM field ?
How close does the photon and EM field have to be for interaction to take place ?
How is it determined that the incoming photon has sufficient energy to jump the electron to a higher energy level? Some kind of information value must be exchanged between the incoming photon and electron.

In other words, some process such as this ...

Photon: Hey, electron ... I'm heading in your direction so get ready.
Electron: Ok, I'm ready to jump if you have sufficient energy to give me.
Photon: No probs ... I have the minimum energy to transfer that you require.
Electron: Ok, roger that ... will be standing by for your minimum approach and have initiated my energy transfer protocols.
Photon: Roger ... confirming matching energy transfer protocols also initiated on my end and standing by ...



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