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Atomic nucleus excited with laser: A breakthrough after decades

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Re: Atomic nucleus excited with laser: A breakthrough after decades

#181

Post by blackoil »

MilStdJunkie wrote: post #149

When you stop and look at QCD in the big picture, it's sort of shocking how little we know - like, really, really know - about the internal structure of the proton, or even the nucleon! It's the curse of "probing" with massive energies. No one's a hundred percent certain of whether they're detecting something that's actually there - like there there - or whether they're looking at by-product of enormous collision ene…

> it's sort of shocking how little we know

To my feeble mind, it's shocking how much we know.

Re: Atomic nucleus excited with laser: A breakthrough after decades

#182

Post by zackmorris »

guidedlight wrote: post #15
dtx1 wrote: post #10

What does "exciting a nucleus" mean?

Thorium-229 has two energy states. A ground state, and an excited isometric state. The laser is used to transition the nucleus from the ground state to the excited isometric state.

25 years ago, there were experiments to move element 72 hafnium (Hf) between its low and excited isomer states, which would allow for the creation of a nuclear battery that could store 100,000 times more energy than a chemical battery, with a 31 year half life, but without neutron release:

https://en.wikipedia.org/wiki/Hafnium_controversy

This would be Iron Man and Star Wars tech if it worked. Unfortunately experiments went dark after 2009, probably because it worked haha, but maybe because Hf is too rare to make a practical battery. So it looks like they tried spalling element 73 Tantalum (Ta), 74 Tungsten (W) and 75 Rhenium (Re) with protons at 90-650 MeV to create 72 Hf with atomic masses 178, 179 and high spin 178m2, 179m2 isomers if I read this right:

https://publications.jinr.ru/record/151982/files/071%28E6-20...

https://apps.dtic.mil/sti/tr/pdf/ADA525435.pdf

There's a lot here though, so I can't really get a clear picture of what the yields are, or simply how many joules it takes to store one joule in an excited isomer. Which is of course all that matters, but papers often leave off the one part we're curious about, forcing us to learn nearly the entirety of the subject matter to derive it ourselves. Although on the bright side, maybe that protects us from nuclear armageddon and stuff.

Maybe someone can fill us in?

Edit: dangit _Microft beat me by 17 minutes, please answer there :-)

Re: Atomic nucleus excited with laser: A breakthrough after decades

#183

Post by [deleted] »

AnimalMuppet wrote: post #130
lordfrito wrote: post #81

Earlier quoted context omitted.

Lol that's a comic book name if I ever heard one. He's only one lab accident away from becoming a super hero/villain.

But then I'm only a name change and a lab accident away. And a name change isn't that hard...

[deleted]

Re: Atomic nucleus excited with laser: A breakthrough after decades

#184

Post by thehappypm »

airstrike wrote: post #121
tzs wrote: post #119

Earlier quoted context omitted.

Note: I will use the term "soccer" for the most common football of Europe, "Association football", and "football" for American football. And before anyone says that soccer fields should be called "pitches" not "fields" I will note that FIFA's "Laws of the Game" call it "field" 184 times. They only mention "pitch" in the glossary where the heading for "field" is "Field of play (pitch)". Generally you want to use Ameri…

> I will use the term "soccer" for the most common football of Europe, "Association football", and "football" for American football. I appreciate your valiant efforts but to my mind this is extra confusing because "soccer" is short for "association football" Time to rename American Football to "handegg" once and for all. Ok, ok, I'll settle for "American Rugby"

I've heard "handegg" before but a football is not shaped like an egg, it's vaguely egg-like but the teardrop shape of an egg is distinctly not what a football looks like.

Re: Atomic nucleus excited with laser: A breakthrough after decades

#185

Post by bawana »

adrian_b wrote: post #97
jhart99 wrote: post #78

Earlier quoted context omitted.

Ahhh thank you! I was wondering why the energy had to be so precise. That makes a ton of sense why it has to be so accurate. What makes this transition so low energy? The only other atomic excited state I have any knowledge of is the iron excited state used in Mossbauer spectroscopy. That transition is much higher energy. Also that one has some coupling to the electronic state of the nucleus. Does this Thorium transi…

The radiation emitted when nuclei transition between their internal energy levels is known as gamma rays. The gamma rays normally have energies per photon many orders of magnitude greater than for visible light and also much greater than for X-rays (which are produced by electrons accelerated by very high voltages when hitting a target). The thorium 229 nucleus is the only one that can emit gamma rays that are so low…

Arent gamma, x, and uv ALL em radiation? What makes a gamma with a wavelength near uv still allow it to be called gamma? Why dont we say the nucleon emits uv at 148 when it transitions to its ground state?

Re: Atomic nucleus excited with laser: A breakthrough after decades

#187

Post by MadnessASAP »

lifeisstillgood wrote: post #51

>>> For example, the Earth's gravitational field could be analyzed so precisely that it could provide indications of mineral resources Hold on how does that work? I have had a sort of sci-fi idea that sufficiently sensitive gravitational field measurements coukd detect the passing of submarines (I am not sure on the maths tbh) - which would render a lot of nuclear strategy moot. Just need to get a grasp on the maths

If you didn't know, deflections in earth's magnetic field are already used to detect submarines, amongst other things. Any large ferrous object will cause a small but detectable deflection in the magnetic field.

Range is pretty short but still large enough that you can do it from an airplane flying over.

Re: Atomic nucleus excited with laser: A breakthrough after decades

#188

Post by bawana »

nullc wrote: post #24

Now how the heck do you generate ~148.38nm light with a narrow linewidth? Their approach using four-wave mixing inherently results in short pulses. .. and given that it decays through gamma emission, does this mean we could now build an optically pumped gamma ray laser?

What i was wondering…exactly… how do you make this kind of a laser? And imagine an xray laser… you could fry the guidance system of drone very precisely

Re: Atomic nucleus excited with laser: A breakthrough after decades

#189

Post by nullc »

karma_pharmer wrote: post #56
M95D wrote: post #34

Earlier quoted context omitted.

The gamma emission would have to re-excite other atoms in a cascade to create a laser. Since the exciting energy is UV, not gamma => no cascade amplification. A "wavelength converter" might be possible. PS: Are you sure it's gamma emission? That takes more energy than the exciting UV photon.

> PS: Are you sure it's gamma emission? That takes more energy than the exciting UV photon. Apparently it is neither: Decay of the 229Th isomeric state of the neutral thorium atom occurs predominantly by internal conversion (IC) with emission of an electron https://www.nature.com/articles/nature17669 https://en.wikipedia.org/wiki/Internal_conversion This is pretty weird. You shine UV light (with exactly the right wav…

Apparently in some ionized states it can't produce the electron and will instead produce the gamma, I'm unclear where the extra energy comes from.

> Almost like an exponentially-discharging solar-powered current source (for a very specific wavelength of "solar").

If one could make the UV source highly efficient perhaps it could be used as a battery with extremely good energy density.

Re: Atomic nucleus excited with laser: A breakthrough after decades

#190

Post by nullc »

LeifCarrotson wrote: post #109
shiandow wrote: post #93

Earlier quoted context omitted.

More to the point >400nm is visible light, this puts 148nm well within the ultraviolet range. Though it's not too far removed from the visible spectrum, wouldn't surprise me if some animals could see it.

148 doesn't feel too far removed from the visible spectrum, but it's in the wrong direction for animals to make use of it. I'm no biologist, but I'd be shocked if there were any animals that had adapted sensitivity to a type of radiation that they are never exposed to in nature. The sun doesn't really emit much UV-C light: https://en.wikipedia.org/wiki/Solar_irradiance#Absorption_an... and the light that is emitted i…

Many animals do have more UV extension than you might initially assume useful: due to scattering following the inverse fourth power of wavelength the sky is lit in the UV a long time before sunrise.

Presumably wouldn't apply anywhere near as far as 148nm since as you note that light doesn't make it to earth.

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