4 ms·
What does "exciting a nucleus" mean?
by dtx1 2y ago
What does "exciting a nucleus" mean?
- atoav 2y agoNot a physicist but "exciting" a thing means to make it oscillate e.g. by adding energy into the system. A violin player is exciting the string of her instrument using a bow. Now in this case they use lasers. I suspect if you choose the right wavelenght (=frequency) of light there is some sort of resonance phenomenom.
- sebws 2y agoThe article mentions switching between "energy states": > This nucleus has two very closely adjacent energy states – so closely adjacent that a laser should in principle be sufficient to change the state of the atomic nucleus. > the correct energy of the thorium transition was hit exactly, the thorium nuclei delivered a clear signal for the first time. The laser beam had actually switched their state. I don't know enough to explain any further.
- gilgoomesh 2y agoApplying energy to lift its electrons across a band gap. In this case, applying 8.35574 electron volts.
- mypalmike 2y agoI thought this was an excitation of the state of the nucleus rather than that of electrons.
- popol12 2y agoYou’re right, parent read too fast
- Turneyboy 2y agoWe know how to do this and have observed this tons of times at this point. This would not be novel in any way. This is about exciting the nucleus which is completely different.
- guidedlight 2y agoThorium-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.
- bboygravity 2y agoAnd then?
- topspin 2y agoAnd then the nuclei return to the ground state. That process is probabilistic and measured in half-lives. The key point is that the decay back to ground state happens at a very precise rate that is not influenced by effectively anything, and can be measured accurately. Thus, a clock.
- dtx1 2y ago> That process is probabilistic and measured in half-lives > The decay back to ground state happens at a very precise rate that is not influenced by effectively anything That sounds contradictory to me.
- topspin 2y agoI suppose it could: the term "probabilistic" applies to the quantum probability of any one metastable isomer (excited nucleus) decaying to ground state. In application you measure large numbers of decays, and in great numbers the decay curve is extremely precise.
- phendrenad2 2y agoIsometric? Like, is the nucleus gaining a virtual proton or something?
- nullc 2y agoNucleons occupy orbital energy states like electrons. The application of energy can shift the state of the nucleus, and some of these alternative states are relatively stable. https://en.wikipedia.org/wiki/Nuclear_shell_model https://en.wikipedia.org/wiki/Nuclear_shell_model
- cshimmin 2y agoIt means getting the nucleus to absorb a certain energy above its ground state. Since it is a quantum object, it can only absorb/emit energy in very specific amounts at once (“quanta”). The details of how the nucleus manifests that extra energy are complicated, but you can imagine it as like, picking up a certain vibrational frequency.
- euroderf 2y agoWith enough absorptions, can the nucleus tear itself apart (i.e. fission) ?
- the8472 2y agoYes, that's one possibility[0]. Or the energy can be sufficient to alter the decay rates of other nuclear reactions (alpha/beta decay, etc.) compared to the base isotope. A weird example: Excited tantalum-180[1] is more stable than its base state. [0] https://en.wikipedia.org/wiki/Photofission https://en.wikipedia.org/wiki/Photofission [1] https://en.wikipedia.org/wiki/Isotopes_of_tantalum#Tantalum-180m https://en.wikipedia.org/wiki/Isotopes_of_tantalum#Tantalum-...
- huytersd 2y agoBut then what happens? Does it expel an electron/release energy etc.?
- greenbit 2y agoProbably just emits another photon of the exact same wavelength a short time later. The time would be probabilistic, like 50% chance of emission in X amount of time.
- graycat 2y agoPhysics does not emphasize this, but the half life concept essentially assumes a Poisson process (Cinlar, Stochastic Processes) which has a Markov (past and future conditionally independent given the present, details from the Radon-Nikodym theorem, with a cute von Neumann polynomial proof, Rudin, Real and Complex Analysis) assumption. The half life concept seems to be standard over much of physics. That a Markov assumption could hold might suggest some new physics.