Induced Fluorescence in a Room-Temperature Gas...

[calbiterol]

I am working on an experiment involving gasses and induced fluorescence. I am under the impression that it is possible to induce fluorescence in certain gasses within the visible spectrum by using an infrared laser or by other means in the non-visible spectrum. Is this correct? If so, with which gasses is this the case?

 

In the little research that I have done about the topic, heavier noble gasses have been brought to my attention, such as Xenon and Argon.

 

The object of my experiment is to produce a small (eventually around the size of a computer pixel, but for now a dot is sufficient) point of visible light in a closed container of gas using induced fluorescence. Under ideal conditions, this would be done with some sort of laser or electron beam. If it is indeed possible to induce fluorescence in a gas in this way, would it also be possible to only excite the atoms in the intersection of two lasers? In other words, would it be possible to use two lasers instead of one, but only have the gas fluoresce where ther lasers met? My only ideas on this have involved something along the lines of using a specific frequency to excite the atom (perhaps its resonant frequency?) and tuning each laser to half of that frequency, so that at their intersection, the full frequency would be reached, and excitation, and therefore fluorescence, will occur. I've thought of numerous problems with this method, though, and I am wondering if there is any other way to produce this effect.

 

 

Please note that I am not particularly knowledgeable in chemistry, as I am only a sophomore in high school -- but also, I am most certainly not doing this for school. If you use anything that is much beyond the configuration of electrons and the basics of atomic theory, please explain it.

 

Any help would be greatly appreciated. Thanks.

[YT2095]

sounds like a plan for a Holograph projector (aka 3D TV).

 

there are chems that will re-emit visible light from an invisible source, UV lasers would be a better choice than IR though (it`s always easier to come down in freq/energy states than to move up)

 

as for the intersection of the 2 beams, that`s more of a Physics question really, I can`t help you there.

[swansont]

You can't get an IR transition to give you a visible photon unless some other interaction also added energy, since IR has less energy than the visible.

 

 

What you'd want is a two-photon transition for the excitation, as you were speculating. On example would occur in Rb-85, where the transition to the first excited state is at 780 nm, and there is another to a higher state at 776 nm (both in the near-IR). A two-photon transition from a 778 nm laser should get you to that state, and it decays part of the time through a different path that includes a 421 nm transition, which is blue.

 

There are many atoms that would do this. There are also some transitions that can only occur with two photons, and could not occur with one of twice the energy, because of conservation laws - photons contain angular momentum, and so the final atomic state cannot have the same value as the initial for one photon absorption, but can for two, since you can have two photons whose angular momentum cancels. An example would be a transition from an "s" orbital to the next higher "s" orbital.

[Hexaditon]

"My only ideas on this have involved something along the lines of using a specific frequency to excite the atom (perhaps its resonant frequency?) and tuning each laser to half of that frequency, so that at their intersection, the full frequency would be reached, and excitation, and therefore fluorescence, will occur. "

 

I'm limited in my knowledge of the physics of these waves and their resonance. But i'd be under the impression that crossing the lasers and causing resonance would just increase the intensity of the light at that point... the frequency wouldn't be altered (am I wrong?). Perhaps a way around this is using more than two. Let's be hypothetical and say... 50 just for emphasis sake. When they all beam in and cross at a single point - the intensity of the beam is sufficiently less everywhere compared to the one point. So that one point is excited to the point where it's noticable over the rest? I don't know. Just trying to help.

 

-Justin

[YT2095]

Cal: you clearly state a "Gas"

 

but wouldn`t using a liquid be a little easier? like the Dyes used in some lasers, that stuff Does jump to an exited state,and would have a greater light density than a gas who`s molecules are scattered around much more.

 

Just a though

[swansont]

I'm limited in my knowledge of the physics of these waves and their resonance. But i'd be under the impression that crossing the lasers and causing resonance would just increase the intensity of the light at that point... the frequency wouldn't be altered (am I wrong?). Perhaps a way around this is using more than two. Let's be hypothetical and say... 50 just for emphasis sake. When they all beam in and cross at a single point - the intensity of the beam is sufficiently less everywhere compared to the one point. So that one point is excited to the point where it's noticable over the rest? I don't know. Just trying to help.

 

-Justin

 

As I stated before, there are transitions that involve the absorption of two photons at once. The frequency of the light isn't altered.

[calbiterol]

Cal: you clearly state a "Gas"

 

but wouldn`t using a liquid be a little easier? like the Dyes used in some lasers' date=' that stuff Does jump to an exited state,and would have a greater light density than a gas who`s molecules are scattered around much more.

 

Just a though [/quote']

 

Would the liquid bend or distort the light either being fluoresced and from the laser (be it ultraviolet, IR, NIR, or anything else)?

 

[Edit: that's a question that is much more appropriate for one of the physics forums, so I moved it over to classical mechanics.]

[calbiterol]

Alright, assuming that a liquid will not distort or bend the light produced too badly, can anyone give me specific names of liquids that will fluoresce like this? I would prefer a colorless liquid... It would be grea if it's excitable by infrared or ultraviolet lasers, but I won't know specifics about that until I ask and recieve an answer in the physics forum about ways of using multiple sources to excite a single point (the whole two-laser deal).

 

 

By the way, thanks for all the help!

 

[Edit: sorry about posting twice in a row - I couldn't see the other posts in the edit window, and I needed to see the other posts to write my question.]

[chemistry]

I would search for common particular experiments rather than try to create one on my own, such experiments have more than enough complications to them. I don't know of any experiments at this point.

[calbiterol]

I would search for common particular experiments rather than try to create one on my own, such experiments have more than enough complications to them. I don't know of any experiments at this point.

 

That's not the point. I'm sure someone has done it before. The point is, I want to do it. Just cause I'm not even in college doesn't mean I'm capable. That never stops me - no matter what it has to do with. If I apply myself, it won't matter how many complications there are, I'll get it done. Point being, I want to do it myself to see exactly what will happen under the circumstances that I create. I don't want to sound like a young and naive kid who is in way over his head and doesn't know it, but I want to do it myself.

[swansont]

That's not the point. I'm sure someone has done it before. The point is, I [/i']want to do it.

 

I don't think that was meant as criticism. I think it was meant as a helpful suggestion - find an experiment that has been done before, and recreate it.

[YT2095]

Would the liquid bend or distort the light either being fluoresced and from the laser (be it ultraviolet' date=' IR, NIR, or anything else)?

 

[Edit: that's a question that is much more appropriate for one of the physics forums, so I moved it over to classical mechanics.']

 

in order...

 

1) there`s no reason to beleive that a liquid will distort anymore than a gas may, in fact a gas is more likely to distort due to molecular dispersal than a liquid is, Also whatever medium you use, it will only "light up" at the point of beam convergence anyway, the real issue to be addressed here would be delay in dropping to a lower energy state!

 

2) good idea, as your question IS a 2 fold one

[calbiterol]

I don't think that was meant as criticism. I think it was meant as a helpful suggestion - find an experiment that has been done before, and recreate it.

 

Sorry, I've been a little jumpy lately. Yes, but the issue there is twofold - I have my own set of unique parameters, one, and two, how exactly would I about finding such an experiment?

[swansont]

how exactly would I about finding such an experiment?

 

Get thee to a library, preferably one that has access to scientific works, though thesedays you may be able to do a bunch of the stuff on Google and searching certain websites. For general stuff Physics Today is a good bet, and would point you toward more specific things. Another resource would be the journal of undergraduate research in physics. I don't know offhand how much searchable stuff there is online for these two.

 

 

But I'm afraid that for some specifics you will have to sort through some physics journals, which will be written at a fairly high level.

[calbiterol]

But I'm afraid that for some specifics you will have to sort through some physics journals, which will be written at a fairly high level.

 

Ai'ight. That's where SFN comes in.