[time-nuts] Exact Rubidium frequency

Peter Vince pvince at theiet.org
Tue Jul 17 14:45:08 EDT 2007

Hello Tom,

	I'd not had a reply from NIST, so was about to write to a 
contact there.  Have they just quietly done it, or did you nudge 
someone?  Anyway, yes, thank you, the table gives the 610.904 figure 
from the French work, but the image still has the old 608 figure on 
it:-(  I had a reply from PTB who agreed their figure was out of date 
and that 610.904 was the currently accepted figure, and promised to 
update the web, but so far they haven't :-(

	Anyway, it's good to get to the bottom of the mystery - 
thanks for your help.  Now I'll just update Wikipedia!


>Hi Peter,
>Do you like the way the NIST page looks now?

>>> Thank you all for your replies.  It still begs the question of why
>>> NIST and PTB disagree by nearly 5 Hz on their web pages - I'll write
>>> and ask them, and report back what they say.
>>> Regards,
>>> Peter Vince  (G8ZZR, London)
>> Peter,
>> Yes, please send a note to NIST and have them update the
>> Rb hyperfine frequency that appears in:
>> http://tf.nist.gov/general/enc-re.htm#rubidiumoscillator
>> My guess is the old ...608 number came from a 1959 paper:
>>  Hyperfine Transitions in Rubidium-87 Vapor
>>  http://tf.nist.gov/timefreq/general/pdf/1537.pdf
>> I suggest for the purposes of their glossary, the new number
>> doesn't have to be accurate to the micro-Hertz and probably
>> doesn't need to be changed every time someone does a new
>> experiment with Rb.
>> NIST gives the defined value for Cesium: 9,192,631,770 Hz
>> and a rounded value for Hydrogen: 1,420,405,752 Hz, so a
>> value of 6,384,682,612 Hz might do. Not sure what to say
>> about ...612.8 vs. ...610.904. Let NIST figure that one out.
>> Either way, I don't have to change my cars ;-)
>>  http://www.leapsecond.com/pages/unix/
>> /tvb

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