American football or European football? This is like the gallon thing all over again.
Or Canadian or Aussie rules football?
Gaelic, obviously
Atomic nucleus excited with laser: A breakthrough after decades
91–100 of 229 posts
Re: Atomic nucleus excited with laser: A breakthrough after decades
#92Earlier quoted context omitted.
Physics like this (really I'd call it materials science; it isn't but it has immediate practical applications on building things) is a bit of a sleeper in terms of importance. Small improvements in tolerances and materials drive huge changes in what is economically feasible at the other end of the science-engineering-machining pipeline. "We've built a higher precision thing" is usually huge news. Take semiconductors,…
This actually has significant practical importance, because it is hoped that using this transition of the thorium nucleus it will be possible to build atomic clocks even better than those using transitions in the spectra of ions or neutral atoms, because the energy levels of the nucleus are less sensitive to any external influences. While in the best atomic clocks one must use single ions held in electromagnetic trap…
What could we do with more accurate atomic clocks that we cannot do with current ones?
Re: Atomic nucleus excited with laser: A breakthrough after decades
#93> If the wavelength of the laser is chosen exactly right ... then maybe a special atomic nucleus could be manipulated with a laser, namely thorium-229. On November 21, 2023, the team was finally successful: the correct energy of the thorium transition was hit exactly, the thorium nuclei delivered a clear signal for the first time. So what's the wavelength? I felt like the article left me hanging. The answer is: 148.3…
Oh that's about 0.0000000014 football fields. More seriously, apparently it takes a photon with a wavelength of 92nm to eject an electron from a hydrogen atom. Maybe this is a reasonable reference/refresher: https://web.archive.org/web/20210413042937/https://www.nagwa...
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.
Re: Atomic nucleus excited with laser: A breakthrough after decades
#94Earlier quoted context omitted.
This actually has significant practical importance, because it is hoped that using this transition of the thorium nucleus it will be possible to build atomic clocks even better than those using transitions in the spectra of ions or neutral atoms, because the energy levels of the nucleus are less sensitive to any external influences. While in the best atomic clocks one must use single ions held in electromagnetic trap…
What could we do with more accurate atomic clocks that we cannot do with current ones?
For interest, Precision Vs Accuracy, Atomic Clocks Vs Sapphire Oscillator
https://news.ycombinator.com/item?id=28232645
Detecting gravity waves with large laser triangles required a few advances in technology - precision clocks was one.
Not so long ago had you asked your question the answer would have been "detect gravity waves".
Re: Atomic nucleus excited with laser: A breakthrough after decades
#95> But it is not just time that could be measured much more precisely in this way than before. For example, the Earth's gravitational field could be analyzed so precisely that it could provide indications of mineral resources or earthquakes This has military applications as well, right? Replacing GPS for nuclear submarines. https://news.ycombinator.com/item?id=29213751 https://news.ycombinator.com/item?id=36222625
My buddy works for such a company, https://www.atomionics.com/ and they are doing pilots with mining companies.
Re: Atomic nucleus excited with laser: A breakthrough after decades
#96> If the wavelength of the laser is chosen exactly right ... then maybe a special atomic nucleus could be manipulated with a laser, namely thorium-229. On November 21, 2023, the team was finally successful: the correct energy of the thorium transition was hit exactly, the thorium nuclei delivered a clear signal for the first time. So what's the wavelength? I felt like the article left me hanging. The answer is: 148.3…
For comparison, over the last several years there has been a lot of research into optical frequency standards. Because they run at a higher frequency than (microwave) caesium frequency standards, optical frequency standards can be more precise. The current candidates https://iopscience.iop.org/article/10.1088/1681-7575/ad17d2 have wavelengths between 750nm and 250nm. Caesium frequency standards use a wavelength of 32.6mm, so about 100,000x bigger than optical frequency standards.
Based on just the frequency, I dunno what makes the thorium nuclear transition much better than optical transitions. Unless the excitement (as it were) is about scaling up to even higher frequencies.
Re: Atomic nucleus excited with laser: A breakthrough after decades
#97From 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.
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 in energy that their energy is not only lower than for X-rays, but it is also lower than for many sources of ultraviolet light. For instance the ultraviolet light used in state-of-the-art lithography for semiconductor manufacturing has much higher frequency (shorter wavelength), by about ten times.
These gamma rays of the Th229 have a wavelength that is not much shorter than the 184-nm ultraviolet light that can be obtained with a mercury-vapor lamp.
What is important is that for such a frequency/wavelength it is possible to build laser sources, which enables the design of an atomic clock that will use thorium 229 nuclei instead of neutral atoms or ions of other elements (like ytterbium, lutetium, strontium, aluminum).
Re: Atomic nucleus excited with laser: A breakthrough after decades
#98Earlier quoted context omitted.
This actually has significant practical importance, because it is hoped that using this transition of the thorium nucleus it will be possible to build atomic clocks even better than those using transitions in the spectra of ions or neutral atoms, because the energy levels of the nucleus are less sensitive to any external influences. While in the best atomic clocks one must use single ions held in electromagnetic trap…
What could we do with more accurate atomic clocks that we cannot do with current ones?
Most units of measurement are derived from the second, so the more precise our frequency standards, the more precise everything else can be. Things like interferometry and spectroscopy depend directly on very precise frequency standards.
Re: Atomic nucleus excited with laser: A breakthrough after decades
#991) does this have any relevance to thorium as nuclear fuel? Looks like no. 2) is there any significance to the units of the wave length? Like they’ve narrowed it down to a number. Does that granularity map to anything? Some sort of discrete scale? Or is there going to be a range of values that work +/- a super tiny value.
This has indeed no relationship with nuclear energy, except that thorium 229 is produced in nuclear reactors.
This achievement is a step (the most important one) towards the goal of making an atomic clock that uses thorium 229 (which has important advantages mentioned in another posting).
Re: Atomic nucleus excited with laser: A breakthrough after decades
#100The 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.
I find it satisfying to see a researcher called THORsten SchUMm devoting his research to THORiUM.
Nominative determinism :-)