Discussion:
Avagadro Number
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c***@optonline.net
2020-12-19 18:52:11 UTC
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Ever so slightly different values are quoted in various references. The value I use is one seen frequently, 6.02214076 E23 . Other perceptions ?
Martin Brown
2020-12-20 13:29:06 UTC
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Post by c***@optonline.net
Ever so slightly different values are quoted in various references.
The value I use is one seen frequently, 6.02214076 E23 . Other
perceptions ?
Unless you are doing something very unusual it makes little difference
beyond 4 sig fig.

Physicists care about it when calibrating the C12 mass scale and ion
counting in mass spectrometry. Chemists tend to just use their results.
--
Regards,
Martin Brown
RichD
2021-01-11 19:49:33 UTC
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Post by Martin Brown
Post by c***@optonline.net
Ever so slightly different values are quoted in various references.
The value I use is one seen frequently, 6.02214076 E23 . Other
perceptions ?
Unless you are doing something very unusual it makes little difference
beyond 4 sig fig.
Physicists care about it when ... ion counting in mass spectrometry
What exactly is ion counting, and how?


Rich
Martin Brown
2021-01-12 11:31:59 UTC
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Post by RichD
Post by Martin Brown
Post by c***@optonline.net
Ever so slightly different values are quoted in various references.
The value I use is one seen frequently, 6.02214076 E23 . Other
perceptions ?
Unless you are doing something very unusual it makes little difference
beyond 4 sig fig.
Physicists care about it when ... ion counting in mass spectrometry
What exactly is ion counting, and how?
Imagine a photomultiplier tube but without the glass envelope and
already in a vacuum chamber. Hit it with an ion at 8kV acceleration and
it spalls a cascade of electrons. You don't need so many gain stages.

There is a limit to how quickly it can recover (dead time) - ours used
to max out at about 10MHz. They can also be run at a much lower gain in
a pseudo analogue sort of way as a current detector.

This lot claim to be up to 1GHz ion count rates now. No idea if it is
genuine and works as advertised. I don't work on that stuff any more.

http://www.cromlab.es/Articulos/SGE/ETP/TA/TA-0103-A.pdf
--
Regards,
Martin Brown
mrou...@shaw.ca
2020-12-20 18:45:58 UTC
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Ever so slightly different values are quoted in various references. The value I use is one seen frequently, 6.02214076 E23 . Other perceptions ?
In the new (2018) SI system, the value of Avogadro's number is fixed (the same way the speed of slight was fixed a few decades ago to define the metre). The value you should use now (and forever) is 6.022 140 76 x 10^{23}, i.e. the one you quoted above. Any other values you might see are historical artifacts now.
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