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Atomic nucleus excited with laser: A breakthrough after decades
221–229 of 229 posts
Re: Atomic nucleus excited with laser: A breakthrough after decades
#222Hey, I'm one of the authors on the paper and see that people are curious about things. I'm happy to answer any questions, cool to find this here!
Re: Atomic nucleus excited with laser: A breakthrough after decades
#223Now 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
One has to first imagine that a photon isn't as immutable as one sometimes believes. Effectively by putting lots of photons together in a medium (the medium makes sure momentum and energy is conserved) one can create all kinds of colors of light. We can already make "lasers" up to x-rays in synchrotrons by using the right means. The definition of laser becomes a bit shady though as the light is coherent and has a small divergence angle, but is not produced through stimulated emission.
Re: Atomic nucleus excited with laser: A breakthrough after decades
#224Earlier quoted context omitted.
> 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.
It doesn't produce an electron, it just donates its energy to one of the electrons bound to it. This energy is then used to free the electron from its bounds and any extra energy is used to give the electron some speed. Effectively the same energy is consumed when emitting the photon or releasing the electron. If the thorium is sufficiently ionized (the more electrons you strip from an atom, the harder it gets to strip the next one), the binding energy of the electrons is so high that the energy from the nuclear excited state is not enough to free the electron and the process is completely blocked from happening.
Re: Atomic nucleus excited with laser: A breakthrough after decades
#225Now 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?
Good question, nobody is sure yet how to do it. Indeed any pulsed laser will result in a broad spectrum (spectrum = inverse of laser pulse time e.g. 1 ns pulse is 1 GHz spectral width). Using frequency combs is a way around this, which are pulsed but the comb teeth are still narrow (approximately 100 Hz). To really go sub Hz one needs to build a continuous wave laser and mostly people are looking towards nonlinear crystals (poled materials, KBBF etc.) to create these using second harmonic generation
Re: Atomic nucleus excited with laser: A breakthrough after decades
#226Very cool. Probably impossible but I wonder if you could see non-linear nuclear effects if you hit it with enough intensity. Laser induced fission anyone?
Look up „hafnium controversy“: https://en.m.wikipedia.org/wiki/Hafnium_controversy
Interesting. Hafnium oxide is my go-to film coating when I want something impervious to etching. That stuff is bomb proof.
31 year half-life gamma emitter is just one more reason to love it!
Re: Atomic nucleus excited with laser: A breakthrough after decades
#227Earlier 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.
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 experimen…
Oh, by all means discuss this here please - your comment is a lot more substantial than my lonely link to Wikipedia.
Re: Atomic nucleus excited with laser: A breakthrough after decades
#228Earlier quoted context omitted.
Can you explain your reply a bit; how will MEG tech evolve from this breakthrough?
I'm still reading the paper but I think it might enable better versions of this sort of thing: https://www.nist.gov/noac/technology/magnetic-and-electric-f...
makes sense, thanks for the link
Re: Atomic nucleus excited with laser: A breakthrough after decades
#229Earlier quoted context omitted.
Nominative determinism :-) https://en.m.wikipedia.org/wiki/Nominative_determinism
Frequency illusion :-P https://en.wikipedia.org/wiki/Frequency_illusion
Not completely. Can't find it now, but there was research cited in the book Alex's Adventures in Numberland showing a real statistical deviation, example: Lawrences' studying Law school more frequently.