Nuclear Clock - 1/20th Second In 14 Billion Yrs - Neutron Orbits Nucleus - Huh? - Page 1
Forum section: electronics / general

author: SgtRock
author_rank: Unknown
timestamp: March 12, 2012, 07:43:27 am
content: Greetings EEVBees:--The Ticktockman will now have a more accurate tool with which to document tardiness. See below link to an article about a proposed Nuclear Clock of extreme accuracy.http://www.sciencedaily.com/releases/2012/03/120308101331.htm--Does anybody understand the part about a neutron orbiting the nucleus?"In the land of the blind, the one-eyed man is king"Desiderius Erasmus Roterodamus 1466 - 1536Best RegardsClear Ether

author: Rerouter
author_rank: Super Contributor
timestamp: March 12, 2012, 10:02:56 am
content: from what i have been able to scrape, (not solid) neutrons have somewhat of an orbit in low density nucli, (suspect very wrong)still being a larger partical i can only assume that is how they get a higher accuracy, as there is less influence of the uncertainty principles (tiny partical such as electron gets a large amount of influence from the methods we use to measure there velocity or position)

author: ejeffrey
author_rank: Super Contributor
timestamp: March 12, 2012, 10:14:30 pm
content: I believe 'neutron' is a word injected by a 'science journalist' to this article. There is no mention of neutrons in the arxiv preprint of this article. It could have been added during the review process or during an interview with the scientists in question.In any case, what is happening here is that the researchers have identified a nuclear isomer transition as a potential clock state, along with a way to drive it and read it out.The way an atomic clock works is that electrons orbiting atomic nuclei exist in only certain allowed configurations, each with a unique energy. There is the ground state which is what we normally encounter, and there are various excited states. Most of the excited states quickly decay to the ground state, but a few of them stick around for quite a while. What an atomic clock does is to drive that transition with a laser or RF source whose frequency is tuned to energy difference between the clock state and the ground state (or a state near the ground state). You need to design a way to tell when you are 'on resonance' or if you are slightly off to one side, and use that to keep your laser on target. Then you simply count the waves of the driving field and that is your clock.Once you sort out all the technical issues, the thing that ultimately limits the accuracy of your clock is basically the frequency of the transition (higher is better), the natural decay time of the excited state (slower is better), and how fast you can drive the transition with your laser (faster is better). Basically the more times you can make it flip from ground to excited and back before it 'accidentially' decays the better.Nuclear isomers are almost just like excited electronic states of an atom. The protons and neutrons fill energy levels grouped into shells. However, nuclear isomers seem to be somewhat uncommon compared to atoms. Most of them exist only as a byproduct of nuclear decay, and quite rapidly decay themselves, either to the ground state by emitting a gamma ray, or by further nuclear decay. In this instance, the excited Th229 isomer can only decay by a UV photon, which gives it a very long lifetime. The lifetime is about 100 times longer than the aluminum ion that holds the current record for lowest imprecision. Basically, an atomic nucleus is so small that it makes a terrible antenna for somethings as big as a UV photon. The long life of this nuclear isomer makes is a candidate for an atomic clock, as long as you have a way to drive it, read it out, and send the result to a counter. Apparently the authors have done just that, although at this point it is a proposal, they haven't actually built one. We can hope to see a few more proposals of next generation atomic clocks and the most promising ones getting built.

author: wkb
author_rank: Super Contributor
timestamp: March 12, 2012, 10:56:34 pm
content: Isotopes, not isomers is what you meant I think.

author: ejeffrey
author_rank: Super Contributor
timestamp: March 12, 2012, 11:24:31 pm
content: Quote from: wkb on March 12, 2012, 10:56:34 pmNo, I meant nuclear isomer.http://en.wikipedia.org/wiki/Nuclear_isomer

author: AntiProtonBoy
author_rank: Frequent Contributor
timestamp: March 13, 2012, 02:35:20 am
content: Very interesting, cheers for the info ejeffrey.