All right, you forum hangers-on

[JIM]

Make yourselves presentable. We might be having guests.
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Unitedheroes.net - We're not lazy, we're... um... productivity-challenged.

[TechnoAtheist]

Quite.

I've put the Pacer on fresh new concrete blocks and even raked the grass.

Well, I dragged that there toothy thing-a-ma-bob over the shorter bits.

It pretty much looks the same, but I found my keys!

(oh, and congrats on the article)
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The Grayhound Chronicles
"TGC is less like a web serial and more like the Al Azif in bite-size form."
--~Steve-o

[Narratio]

I'm shuffling the hangers on over to Moe's Barbers, Tuxedo hire and bait shop. We'll have spiffy hair cuts, neat jackets and a good mess o'catfish for when your guests come!

Ummmm, Maracus wants to know if "Mossbauer Spectroscopy" comes under the heading of knowing more and more about less and less?
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Age and cunning will always beat youth and talent.

[JIM]

Yes.
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Unitedheroes.net - We're not lazy, we're... um... productivity-challenged.

[steveo]

Does this mean no more frog baseball?
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Shihan of Martial Arts Sandwich Making and author of Christopher Ford, Amateur Paranormalist

[JIM]

Oh no, frog baseball is totally <i>on</i>. Just make sure you wear a tie.

Not the one with the blinking LEDs though.
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Unitedheroes.net - We're not lazy, we're... um... productivity-challenged.

[Maracus]

I'm not sure what Narratio is talking about. But sure. And I already had a hair-cut, though I should probably shave before they drop by.
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Those who ask themselves "why?", to the same questions are lacking in creativity. Make something up.

[Narratio]

I locked the doors to the cat bowling alley and put the alligator back under the sink. Can't get the carpet cleaned though, the pest exterminator can't come by till next wednesday. And we owe him for the giant roach job.
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Age and cunning will always beat youth and talent.

[bobthegoat]

Okay, so admittedly my nuclear physics is a bit shakey (having only made it through second semester physics for engineers and a computational physics class that was esstentially Numerical Methods in C's first few chapters), but this recoiless gamma ray thing strikes me as odd. I mean, even at the nuclear level, F still equals m*a, so even though relative masses between photons and a lump of radioactive isotope is massive, there will still be some quantifiable force applied to the isotope (equal and opposite reaction and all that). How is this damped, by the Mossbauer effect (which I didn't even know about until ~5 min ago), or some other means.

Come on, you're a grad student, you should be used to enlightening moronic people who only nominally want to acquire information.
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Bob the Goat: All the goat with none of the Malevolence

[JIM]

Oh my goshorz, someone asked a question related to my thesis! NOW YOU SHALL ALL SUFFER!

Suppose you're shootin' gamma rays at a material. (No, it doesn't turn green when it gets angry.) If a photon hits an atomic nucleus, two things can happen. In most cases, it'll bounce off ("scatter") but if the photon is of just the right energy the nucleus can absorb the photon and hop up to a higher energy state. (Imagine the protons and neutrons are vibrating in the nucleus, and after absorbing the photon they're vibrating faster.)

Now, "just the right energy" means the difference between the higher and starting states of the nucleus, <i>plus</i> energy the nucleus uses in recoiling during the absorption. (Just like you recoil when you absorb a water balloon somebody chucks at you.) But this recoil energy depends on the momentum of the nucleus immediately before the absorption, which is <i>impossible</i> to know because it's the result of thermal vibration and good ol' Heisenburg quantum fluctuations. And this unknown recoil energy is orders of magnitude bigger than the difference in nuclear energy levels that you want to look at. So, not much use there.

That's the case when you're hucking gamma rays at a gas. <b>But</b>, if it's a solid, each atom in the sample is attached to its neighours by stiff chemical bonds. Now for a certain fraction of the atoms in the sample, the recoil of the nucleus when it absorbs a photon is effectively distributed through the <i>entire sample</i> over the chemical bonds, so that the recoil of the nucleus is negligible compared to the the difference in nuclear energy levels that you want to look at. This is the "Mössbauer effect".

Kind of a little bit like how a Kevlar bullet proof vest works, I suppose, only much better.

Now you know... and knowing is half the battle!
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Unitedheroes.net - We're not lazy, we're... um... productivity-challenged.

[Maracus]

Coolness abounds. I do have a question though. If you can add protons to the nucleus, and electrons to the orbit, can you change one element into another, or is there more to it?
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Those who ask themselves "why?", to the same questions are lacking in creativity. Make something up.

[JIM]

Nope, that's pretty much it. But adding protons to a nucleus is non-trivial.
That is, in non-science-speak, really really really hard.
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Unitedheroes.net - We're not lazy, we're... um... productivity-challenged.

[Maracus]

Is it possible to "build" an element from a combination of protons, neutrons, etc?
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Those who ask themselves "why?", to the same questions are lacking in creativity. Make something up.

[TechnoAtheist]

Sure. Stars do it all the time. It just takes quite a bit of effort and you don't want to be around when it happens.

Which explains why folks like Paris Hilton leak helium and silicone.
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The Grayhound Chronicles
"TGC is less like a web serial and more like the Al Azif in bite-size form."
--~Steve-o

[TSGarp]