[time-nuts] Re: Creating a D.I.Y Rubidium Atomic Clock

[Magnus Danielson]

Hi Rick,

Yes. The D1 and D2 lines of Rb87 and Rb85 align up so you can use Rb85 
as filter for the Rb87 to get a more efficient optical pumping of the 
Rb87 gas cell. It is mainly this property that enabled rubidium to be 
the primary gas cell atom & isotope, that enabled a much cheaper 
physical package. Today you could potentially replace the Rb85 filter 
cell with modern optical filters. The Rb85 filter is really just part of 
the lamp, but in practice many have a mix of Rb85 and Rb87 in the 
reference cell.

Then again, replace the filter with a laser diode for 780 nm that is 
steered up to the right wavelength, and you avoid the filtering 
altogether. That has a few issues of itself naturally, but they can be 
solved and is so for modern setups. Then you can use some completely 
different spieces, and look at them CSACs doing this with cesium instead.

It is interesting how very specific details steer what type of clocks is 
built. There where rubidium and thallium beams too, but they became less 
meaningful as cesium was selected. But then again, rubidium became 
popular for the folded beam-tube called fountain. Thallium could have 
been our reference, but it was harder to ionize and it was harder to 
produce the 24 GHz frequency for, so it was not very easy to replicate, 
but those drawbacks is gone with todays RF and laser technologies.

One thing which our normal rubidiums does not handle well is the 
amplitude of optical pumping field as well as RF field will cause AC 
Stark frequency shift, those providing a mechanism for low frequency 
drift. Stabilizing these with servo loop could be among the things one 
can have a look at if one fool around.

Cheers,
Magnus

On 2023-06-07 23:45, Richard Karlquist via time-nuts wrote:
> My understanding is that the Rb85 and Rb87 isotopes happen to
> accidentally be correct to make the optical filter cell work correctly.
> I don't believe you can do this with any other atom.  It's different
> from primary atomic standards that just excite the hyperfine quantum
> transition.  In that case, you can debate about which atom or ion to
> use.
>
> ---
> Rick Karlquist
> N6RK
>
> On 2023-06-07 13:37, Marek Doršic via time-nuts wrote:
>
>>> On 7 Jun 2023, at 20:37, djl via time-nuts <time-nuts at lists.febo.com> wrote:
>>> Certainly interesting topic. Rb provides a safe approach. However, I am curious to know if anyone has explored the possibility of using other elements, specifically Indium?
>>>
>>> .md
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