A more precise atomic mass of ^4He : Ongoing reduction of uncertainties for the UW-PTMS
Abstract
Using a Penning trap mass spectrometer (PTMS), the atomic mass of ^4He has been found to be 4 002 603 254.153(64) nu (an uncertainty of 16 ppt). This number agrees well with the previous two best measurements of the ^4He mass(S. Brunner, et al., Eur. Phys. J. D 15), 181-188 (2001). (T. Fritioff, et al., Eur. Phys. J. D 15), 141--143, (2001).. In addition to giving a precise atomic mass of the α-particle, ^4He can now be used as a convenient reference ion by less precise mass spectrometers. For our measurement, the cyclotron frequencies of ^12C^6+ and ^4H^2+ ions were compared, using a Penning ion trap with an extremely stable (less than 2 ppt/h of drift) magnetic field. While many aspects of our experiment have been previously described (as for the recent ^16O result, at 10 ppt unceratinty(R. S. Van Dyck, Jr., S. L. Zafonte, and P. B. Schwinberg, Hyp. Interact. 132), 163--175, (2001), and references.), we will present several techniques and changes to the apparatus that have improved the accuracy of our machine by about an order of magnitude in recent years.
- Publication:
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APS Division of Atomic, Molecular and Optical Physics Meeting Abstracts
- Pub Date:
- May 2004
- Bibcode:
- 2004APS..DMP.S4003P