Re: [time-nuts] Is 5061A by itself a primary reference? Was: Modern Rb atomic reference vs classic Cs
richard@karlquist.com said:
At one time, only cesium standards were considered truly primary because of
the definition of the second. However, the quantum mechanical constants of
other atoms such as Rb have been measured to much more accuracy than the 5071
so that Rb standards can be considered traceable to Cs if they are otherwise
of primary architecture. The key idea is that all Rb atoms are absolutely
identical. Rb gas cells are of course never primary.
Can the physics-nuts calculate the Rb frequency relative to Cs?
What's missing on a gas cell? Is the problem theory or implementation?
--
These are my opinions. I hate spam.
On 3/14/2020 1:57 PM, Hal Murray wrote:
richard@karlquist.com said:
At one time, only cesium standards were considered truly primary because of
the definition of the second. However, the quantum mechanical constants of
other atoms such as Rb have been measured to much more accuracy than the 5071
so that Rb standards can be considered traceable to Cs if they are otherwise
of primary architecture. The key idea is that all Rb atoms are absolutely
identical. Rb gas cells are of course never primary.
Can the physics-nuts calculate the Rb frequency relative to Cs?
I used to wonder about why there isn't a formula for calculating
the transition frequencies for an atom, at least relative to
another variety, but I know almost nothing about quantum mechanics.
Evidently, if it were possible, we would have heard about it by now.
What's missing on a gas cell? Is the problem theory or implementation?
The buffer gas shifts the frequency depending on pressure and
temperature. There apparently isn't any reasonable way to sense
the pressure in the cell. Also, there is "light shift" that can't
be eliminated, etc. When I worked on the HP 10816 40 years ago,
there was "power shift" from the RF. There may be a way now to
finesse that away. Anyway, theory doesn't support the idea
that it's just implementation that is the panacea.
As far as implementation goes, that depends on suitable lasers,
which weren't around in those days. Even then, you have doppler
shift, unless you use cold atoms. Etc.
Rick N6RK
At one time, only cesium standards were considered truly primary because
of
the definition of the second. However, the quantum mechanical
constants of
other atoms such as Rb have been measured to much more accuracy than
the 5071
so that Rb standards can be considered traceable to Cs if they are
otherwise
of primary architecture. The key idea is that all Rb atoms are
absolutely
identical. Rb gas cells are of course never primary.
FWIW BIPM just recently started publishing a graph like this that shows
monthly TAI-contributions from what BIPM considers primary frequency
standards (Cs beam and fountains) as well as 'SRS'-clocks (secondary
representation of the second):
https://webtai.bipm.org/database/show_psfs.html
for these contributions they require a published uncertainty-budget where
you calculate 'on paper' all the known shifts and show how you have
controlled them to give a total uncertainty of the clock.
Can the physics-nuts calculate the Rb frequency relative to Cs?
I used to wonder about why there isn't a formula for calculating
the transition frequencies for an atom, at least relative to
another variety, but I know almost nothing about quantum mechanics.
Evidently, if it were possible, we would have heard about it by now.
I think there might be around 12 digits (?) or so of agreement between
theory and experiment for Hydrogen (and anti-Hydrogen!?) - but for the
complex clock atoms I think there's no theory that predicts the transition
frequencies very well.
On Sat, 14 Mar 2020 13:57:21 -0700
Hal Murray hmurray@megapathdsl.net wrote:
What's missing on a gas cell? Is the problem theory or implementation?
I just stumbled over this sentence in [1]:
---schnipp---
The shift of the Rb-hyperfine center frequency νRb resulting from buffer
gas pressure (2.6 kPa) is measured as 3390 Hz, this is in excellent
agreement with theoretically estimated value of 3385 Hz.
---schnapp---
Attila Kinali
[1] "Compact High-Performance Continuous-Wave Double-Resonance Rubidium
Standard With 1.4 × 10−13 τ −1/2 Stability" by Bandi, Affolderbach,
Stefanucci, Merli, Skrivervik, and Mileti, 2014
https://doi.org/10.1109/TUFFC.2013.005955
--
<JaberWorky> The bad part of Zurich is where the degenerates
throw DARK chocolate at you.
The paper "Compact High-Performance Continuous-Wave Double-Resonance
Rubidium Standard With 1.4 × 10−13 τ −1/2 Stability" can be found
here:
http://www.unine.ch/files/live/sites/ltf/files/shared/Publications/2014/2014_IEEE_Trans_UFFC_61_1969-1978.pdf
On Thu, Mar 19, 2020 at 11:26 AM Attila Kinali attila@kinali.ch wrote:
On Sat, 14 Mar 2020 13:57:21 -0700
Hal Murray hmurray@megapathdsl.net wrote:
What's missing on a gas cell? Is the problem theory or implementation?
I just stumbled over this sentence in [1]:
---schnipp---
The shift of the Rb-hyperfine center frequency νRb resulting from buffer
gas pressure (2.6 kPa) is measured as 3390 Hz, this is in excellent
agreement with theoretically estimated value of 3385 Hz.
---schnapp---
Attila Kinali
[1] "Compact High-Performance Continuous-Wave Double-Resonance Rubidium
Standard With 1.4 × 10−13 τ −1/2 Stability" by Bandi, Affolderbach,
Stefanucci, Merli, Skrivervik, and Mileti, 2014
https://doi.org/10.1109/TUFFC.2013.005955
--
<JaberWorky> The bad part of Zurich is where the degenerates
throw DARK chocolate at you.
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