Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Atomic nucleus excited with laser: A breakthrough after decades

tuwien.at

Post reply on HN
Print view View original

121–130 of 229 posts

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

#121

Post by airstrike »

tzs wrote: post #119
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 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"

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

#122

Post by denton-scratch »

emblaegh wrote: post #7
danans wrote: post #2

> This makes it possible to combine two areas of physics that previously had little to do with each other: classical quantum physics and nuclear physics. Is quantum physics now considered part of classical physics? If so then man, time flies!

Classical there is used in the sense of “non relativistic”.

I thought relativistic quantum physics was not a thing (yet).

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

#123

Post by NateEag »

beretguy wrote: post #115
pmayrgundter wrote: post #76

Earlier quoted context omitted.

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.

But better would be a prog-rock album named:

Supravisiblue

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

#124

Post by pfdietz »

lordfrito wrote: post #81
tromp wrote: post #79

Earlier quoted context omitted.

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

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.

And he's working with a dangerous radioactive isotope!

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

#125

Post by pfdietz »

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.

The Q of nuclear transitions is just insane (as reflected by their long half life, something in excess of 1700 seconds here for free atoms.) The uncertainty relationship is normally written as delta-p delta-x > hbar/2, but it can also be written as delta-t delta-E > hbar/2. So, if the half life is very long, delta-E can be very small.

This fact is used in Mössbauer spectroscopy (recoilless gamma emission in solids). The peak is so sharp that it was famously used by Pound and Rebka to detect the gravitational red shift in the lab at Harvard in 1960, reaching 1% accuracy by 1964.

https://en.wikipedia.org/wiki/Pound%E2%80%93Rebka_experiment

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

#126

Post by pfdietz »

phendrenad2 wrote: post #23
guidedlight wrote: post #15

Earlier quoted context omitted.

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.

Isometric? Like, is the nucleus gaining a virtual proton or something?

The correct word is "isomeric", as in the state of a nuclear isomer.

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

#127

Post by kingkawn »

pfdietz wrote: post #124
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.

And he's working with a dangerous radioactive isotope!

We’re so close! Send some spiders into the reaction chamber!

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

#128

Post by Galatians4_16 »

tzs wrote: post #119
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 Ameri…

European soccer, or American soccer? (there are significant differences)

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

#129

Post by CamperBob2 »

fanf2 wrote: post #96
cantrevealname wrote: post #9

> 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…

The key factor is the line width, or the range of frequencies over which the transition can be stimulated. The ratio of the stimulus frequency and line width is one way of expressing the resonator Q factor. In general, the lower the line width for a given transition, the higher the Q, the better the signal-to-noise ratio, and the more stable the resulting clock. (Imagine how much more precisely the frequency of a large bell could be measured compared to a cymbal or something else with a broader acoustical spectrum.)

Cs or Rb clocks give you a line width of a few hundred Hz at 9 GHz (Q=roughly 100 million), while quantum transitions in optical clocks can achieve line widths on the order of 1 Hz in the PHz region (equivalent Q in the quintillions.) There is a lot more to building a good clock than high Q, but it's a very important consideration ( http://www.leapsecond.com/pages/Q/ ).

What caught my eye is the ringdown time of the stimulated optical resonance, apparently in the hundreds of seconds. They talk about line widths in the GHz range, but that seems to refer to the laser rather than the underlying resonance being probed. It would have been interesting to hear more about what they expected regarding the actual transition line width. Probably the information is there but not in a form that I grokked, given insufficient background in that field.

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

#130

Post by AnimalMuppet »

lordfrito wrote: post #81
tromp wrote: post #79

Earlier quoted context omitted.

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

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...
Post reply on HN