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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

#111

Post by shiandow »

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…

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.

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

#112

Post by defrost »

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.

Does it?

Inversion is rarely unique, and it's not due to the precision with which the field is measured.

https://earthsciences.anu.edu.au/study/student-projects/nove...

https://inside.mines.edu/~rsnieder/snieder_trampert_00.pdf

Epilogue:

    Linear inverse problem theory is an extremely powerful tool for solving inverse problems. Much of the information that we currently have on the Earth’s interior is based on linear inverse problems

    Despite the success of linear inverse theory, one should be aware that for many practical problems our ability to solve inverse problems is largely confined to the estimation problem.

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

#113

Post by twic »

mananaysiempre wrote: post #90
tromp wrote: post #79

Earlier quoted context omitted.

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

For what it’s worth, the names of both the element and the researcher do in fact refer to the Norse god of thunder Thor.

Even better, Thorsten = Thor's stone!

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

#114

Post by twic »

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…

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 absorbs at ~165 nm, a benzene ring at ~180 nm, and building things out of those tends to increase the wavelength, not decrease it. 148 nm is single bond territory - could you have a chromophore which uses photons of the right wavelength to break a bond, and then somehow react to the presence of free radicals?!

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

#115

Post by beretguy »

pmayrgundter wrote: post #76
whatshisface wrote: post #37

Earlier quoted context omitted.

148nm is on the lower end of UV-C. It's higher-energy than the furthest ultraviolet light that the sun produces (200nm). If it were produced artificially, it'd be heavily absorbed by the atmosphere to the point of near opacity. If the visible spectrum was an octave, where the "tone" of a color wrapped around from red back to blue the way G wraps to A, it'd be the blue one octave above visible blue.

Nice to hear the octave relation used! "blue above visible blue" is a good name.. hmm, a little web tool to name these would be neat ;)

> "blue above visible blue"

Good name for a rock band. Or some tv series.

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

#116

Post by baybal2 »

jncfhnb wrote: post #83

1) 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.

[dead]

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

#117

Post by denton-scratch »

adrian_b wrote: post #89
roenxi wrote: post #60

Earlier 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…

> 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 influences might introduce unwanted uncertainty. But I'd like to know what the claim for greater accuracy is based on, rather than simply greater reliability.

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

#118

Post by acidburnNSA »

jncfhnb wrote: post #83

1) 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.

Not yet. But if someone could condition nuclear fuel atoms so that when they do fission, they consistently break into one delayed neutron precursor and one stable or near stable atom with no long-term afterglow heat, that could revolutionize nuclear power. I've been told that this dream is impossible but it's still my 1 genie wish. Right now they break into 50% of the periodic table and cause all sorts of grief.

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

#119

Post by tzs »

thebruce87m wrote: post #65

American football or European football? This is like the gallon thing all over again.

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 American football fields for this because American football fields have a standard size, 100 yards x 160 feet (91.44 x 53.3 meters). That size field is used in professional, college, and high school football.

Soccer fields on the other hand not only vary from country to country, they aren't even always all the same size within a league. The English Premier League for example is trying to standardize on 105 x 68 meters but several clubs are not yet there: Brentford (105 x 65), Chelsea (103 x 67), Crystal Palace (100 x 67), Everton (103 x 70), Fullham (100 x 65), Liverpool (101 x 68), and Nottingham Forest (105 x 70).

For international play the standard is a range. 100-110 meters length and 64-70 meters width.

There are parts of soccer fields that are standardized to specific values rather than ranges so would be good for unambiguous length or area comparisons. The amusing thing is that those all have fractional values in metric but integer values in Imperial/US units:

• Radius of circle around center mark: 10 yards.

• Penalty area: 44 x 18 yards.

• Distance from penalty mark to goal: 12 yards.

• Goal area: 20 x 6 yards.

• Distance between goal posts: 8 yards.

• Height of crossbar: 8 feet.

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

#120

Post by twic »

jhart99 wrote: post #78
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.

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…

I found a paper which measured the energy of the transition [0], but it doesn't talk about why it's so low. Might be a starting point if you have more time to read than i do, though!

EDIT Hmm [1]:

> Interestingly, the existence of a nuclear excited state of such low energy seems to be a coincidence and there is currently no conclusive theoretical calculation that allows to predict nuclear levels to this precision.

And there is a paper with a ton of detail and some nice diagrams of energy levels [2], but i'm not sure it really gets at "why".

[0] https://arxiv.org/abs/1905.06308

[1] https://link.springer.com/article/10.1140/epja/s10050-020-00...

[2] https://iopscience.iop.org/article/10.1088/1361-6455/ab29b8

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