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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

#151

Post by JanisErdmanis »

btilly wrote: post #110
defrost wrote: post #105

Earlier quoted context omitted.

> These clocks could be sufficiently precise to find mineral deposits underground from their gravity signature. We've been doing that since the 1960s at least with such things as the LaCoste & Romberg gravimeter (1936). You can download, see online the "Geoid" https://americanhistory.si.edu/collections/nmah_865074 https://en.wikipedia.org/wiki/Gravimetry https://en.wikipedia.org/wiki/Geoid Magnetic anomalies also hig…

Yes, but a better clock means more precise measurements, means we can locate smaller masses to higher precision.

The problem is that the planet could be hollow and produce the same gravitational measurements on the surface and outside. It needs to be coupled with a model that introduces constraints for the inverse problem to be defined.

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

#152

Post by BenjiWiebe »

narag wrote: post #146
twic wrote: post #114

Earlier quoted context omitted.

Also, even if there was some advantage to doing so, i'm not sure how animals could see a wavelength that short. They would need a photoreceptor protein which can absorb photons of that wavelength and turn them into some sort of chemical change which can trigger a signalling cascade. That protein would have to have a pair of molecular orbitals which are h * 148 nm apart. What can give you that? The ethene double bond…

A long time ago I saw some UV photos of flowers, compared to visible and IR. There were some distinct features. That suggests some insects could see them, but of course it's just speculation.

That would be UV-A, I believe. Not UV-C.

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

#153

Post by tomxor »

davnicwil wrote: post #100
tromp wrote: post #79

Earlier quoted context omitted.

I find it satisfying to see a researcher called THORsten SchUMm devoting his research to THORiUM.

Nominative determinism :-) https://en.m.wikipedia.org/wiki/Nominative_determinism

Frequency illusion :-P

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

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

#154

Post by ChrisClark »

andrewflnr wrote: post #143
tlb wrote: post #4

From the paper, the light is UV-C at around 140nm or 8.4 eV. But it has to be very precisely the right energy to cause the transition, since nuclear states don’t have any place to dump excess energy to.

Where do electron transitions usually dump excess energy?

Don't they usually create a photon with that energy?

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

#155

Post by [deleted] »

fsh wrote: post #5

The measurement was already confirmed by a different group: https://arxiv.org/abs/2404.12311 This is important since impurities in the crystals used lead to all kinds of fluorescence that could be mistaken for a signal from the Thorium ions. Now two groups have seen exactly the same signal in different Thorium-doped crystals which is very covincing that they have found the actual nuclear transition.

[deleted]

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

#156

Post by blincoln »

narag wrote: post #146
twic wrote: post #114

Earlier quoted context omitted.

Also, even if there was some advantage to doing so, i'm not sure how animals could see a wavelength that short. They would need a photoreceptor protein which can absorb photons of that wavelength and turn them into some sort of chemical change which can trigger a signalling cascade. That protein would have to have a pair of molecular orbitals which are h * 148 nm apart. What can give you that? The ethene double bond…

A long time ago I saw some UV photos of flowers, compared to visible and IR. There were some distinct features. That suggests some insects could see them, but of course it's just speculation.

It's not speculation. Bee eyes have receptors for green, blue, and UV-A light, for example. But as BenjiWiebe mentioned, that's not the same as being sensitive to UV-C.

I'm sure there would be some value in seeing others parts of UV. Some minerals fluoresce from one type of UV light but not another, so they'd be dark in the bands that cause them to fluoresce. Mantis shrimp can apparently see into UV-B, but I'm not aware of anything living that can see UV-C.

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

#157

Post by smegger001 »

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"

Or just go back to calling it gridiron football.

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

#158

Post by [deleted] »

fsh wrote: post #5

The measurement was already confirmed by a different group: https://arxiv.org/abs/2404.12311 This is important since impurities in the crystals used lead to all kinds of fluorescence that could be mistaken for a signal from the Thorium ions. Now two groups have seen exactly the same signal in different Thorium-doped crystals which is very covincing that they have found the actual nuclear transition.

[deleted]

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

#159

Post by pfdietz »

shiandow wrote: post #111
LeifCarrotson wrote: post #109

Earlier quoted context omitted.

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…

Ah, yeah makes sense that animals couldn't see it if it's not really part of sunlight. I was thinking it was not physically impossible, but it would be remarkably pointless if the light is simply not there.

I don't see how it could get into an organism if it's absorbed by air and water.

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

#160

Post by pfdietz »

wbl wrote: post #134
denton-scratch wrote: post #117

Earlier quoted context omitted.

> clocks even better than those using transitions in the spectra of ions or neutral atoms I'd be interested to know how much more accurate a nuclear-state-transition clock might be than a conventional Caesium or Rubidium clock. TFA seems to make the point that a nuclear clock would be more resistant to external influences, such as EM radiation, than an atomic clock, and so could be used in experiments where such infl…

You have the math turned around. Because the nuclear resonance is much more stable and high frequency the Q factor and accuracy of the measurement is higher. With a cesium or rubidium clock it's very difficult to control all the influences on how tightly the nominal resonance is achieved and the Q while impressive is a bit less. There are some real challenges in realization: this will take optical combs and all sorts…

They also point out that because the thorium atoms can be embedded in a solid, and have motion << the wavelength of the radiation, the emission and absorption are largely recoil-free. This eliminates Doppler broadening. What broadening there could be was below the resolution of their pump beam.
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