Path: ...!news.mixmin.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Phil Hobbs Newsgroups: sci.electronics.design Subject: Re: OT: Atomic nucleus excited with laser: a breakthrough after decades Date: Wed, 8 May 2024 14:45:42 -0000 (UTC) Organization: A noiseless patient Spider Lines: 80 Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Injection-Date: Wed, 08 May 2024 16:45:42 +0200 (CEST) Injection-Info: dont-email.me; posting-host="7dede5158803948320989357a9d66ded"; logging-data="32335"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18u6SP9jq/1HdjqkzMqKea3" User-Agent: NewsTap/5.5 (iPhone/iPod Touch) Cancel-Lock: sha1:T/zpMLswLrRV8DlJPRph2+PNhGM= sha1:Sl4xeMxuYtF1/WnKowJgEOBESyc= Bytes: 4566 Martin Brown <'''newspam'''@nonad.co.uk> wrote: > On 08/05/2024 09:44, Jeroen Belleman wrote: >> On 5/8/24 01:36, John Larkin wrote: >>> On Tue, 07 May 2024 12:17:24 -0400, Joe Gwinn >>> wrote: >>> >>>> On Tue, 7 May 2024 16:26:27 +0200, Jeroen Belleman >>>> wrote: >>>> >>>>> On 5/7/24 15:35, Martin Brown wrote: >>>>>> On 07/05/2024 06:06, Jan Panteltje wrote: >>>>>>> Atomic nucleus excited with laser: a breakthrough after decades >>>>>>> ÿÿ >>>>>>> ÿÿÿ The 'thorium transition', which has been sought after for >>>>>>> decades, >>>>>>> ÿÿÿ has now been excited for the first time with lasers. >>>>>>> ÿÿÿ This paves the way for revolutionary high precision technologies, >>>>>>> including nuclear clocks >>>>>> >>>>>> I wonder what the Q value for stimulated nuclear emission is? >>>>>> >>>>> >>>>> They state a centre frequency of roughly 2 PHz and a decay time >>>>> of 630s, which would put the Q in the 1e19 ballpark. Prodigious. >>>>> No wonder it was hard to find. >>>> >>>> The Time guys have been looking for this forever, so to speak. >>>> >>>> It's the only atomic kernel transition with any degree of coupling to >>>> electromagnetic radiation.ÿ This will be orders of magnitude better >>>> than such as lattice clocks. >>>> >>>> There will be a flood of papers. >>>> >>>> Joe Gwinn >>> >>> They aren't tuning to a resonance, but to the difference between two >>> close resonances. >> >> The current definition of the second uses something similar: Some >> hyperfine resonance of cesium. Normal resonances are in the optical >> domain, but hyperfine ones are RF. > > Which puts them in the RF frequency domain where counting cycles of the > continuous sine reference waveform is relatively easy. > > Likewise for H-maser another favourite local time reference signal. > >> In nuclei, normal transitions are in the gamma domain, and >> hyperfine ones are in the domain of optics. It's just a change >> of scale, if you will. > > Although there will be some big practical difficulties counting cycles > of a waveform at 8eV which is up into the UV. What is the current > highest frequency that a semiconductor divider is capable of accepting? > > I know that there are some optical logic circuits about but how capable > are they at near UV light? > > You can't mix this thing down without losing its fidelity. I know how to > double optical frequencies but how do you halve or quarter them? > You mix with an optical frequency comb, possibly with an intermediate locking step. The cleverest part of the Hall-Haensch comb generator is that you can lock the blue end of the comb to the second harmonic of the red end, one tooth off, and lock the difference to a good reference. Then all the teeth have the same phase noise as the reference oscillator, rather than 20 log(600 THz / 100 MHz) ~ 138 dB worse, as it would be in a multiplier. That 0.002 Hz line width is going to make the locker design entertaining. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics