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Analytical Chemistry

Weighing the proton

More precise measurements suggest that the subatomic particle is lighter than previously thought

by Jyllian Kemsley
July 24, 2017 | APPEARED IN VOLUME 95, ISSUE 30

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Sources: H. Borgenstrand, Ph.D. thesis, Stockholm University, 1997; AIP Conf. Proc. 1999, DOI: 10.1063/1.57450; Phys. Scr. 2002, DOI: 10.1238/Physica.Regular.066a00201; Phys. Rev. A 2008, DOI: 10.1103/PhysRevA.78.012514; International Council for Science Committee on Data for Science & Technology, 2014; Phys. Rev. Lett. 2017, DOI: 10.1103/PhysRevLett.119.033001.
Sources: H. Borgenstrand, Ph.D. thesis, Stockholm University, 1997; AIP Conf. Proc. 1999, DOI: 10.1063/1.57450; Phys. Scr. 2002, DOI: 10.1238/Physica.Regular.066a00201; Phys. Rev. A 2008, DOI: 10.1103/PhysRevA.78.012514; International Council for Science Committee on Data for Science & Technology, 2014; Phys. Rev. Lett. 2017, DOI: 10.1103/PhysRevLett.119.033001.

The proton may be significantly lighter than currently believed—1.007276466583 amu compared with 1.007276466879 amu—reports a group led by physicist Sven Sturm of the Max Planck Institute for Nuclear Physics (Phys. Rev. Lett. 2017, DOI: 10.1103/PhysRevLett.119.033001). A lower proton mass could affect the values of physical constants such as the Rydberg constant, which represents the lowest-energy photon that can ionize a hydrogen atom from its ground state. The scientists used a Penning trap, which holds a proton in a combination of magnetic and electric fields. The frequency at which the proton orbits in the magnetic field is proportional to its charge-to-mass ratio.

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Comments
Hyperfuzzy (July 26, 2017 2:06 PM)
The proton is monopolar and gravity is a multipolar response. Existence Proof: There only exist the polar fields, the proton and the electron; more precisely the diametrical spherical fields, never created or destroyed. ...
David (July 26, 2017 4:11 PM)
Precise or accurate measurements? There's a difference.
Rama Viswanathan (July 27, 2017 6:27 PM)
To be fair to the writer of the article,the std deviation pictorial provided as an inset in the article indicates that the measurement is _certainly_ more precise and _probably_ more accurate if the model/method used is more refined...
J-F Gal (July 27, 2017 10:31 AM)
"amu" (atomic mass unit) is no longer in use. The correct symbol is "u".
Jyllian Kemsley (July 30, 2017 4:58 PM)
I was not aware! I've asked our copy editor to consider changing it in our style guide.
Hyperfuzzy (August 4, 2017 6:52 PM)
The proton is monopolar and gravity is a multipolar response. Existence Proof: There only exist the polar fields, the proton and the electron; more precisely the diametrical spherical fields, never created or destroyed. ...

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