[time-nuts] Exact Rubidium frequency

Tom Van Baak tvb at LeapSecond.com
Tue Jul 17 04:56:26 EDT 2007

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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