Penning trap mass measurements of the deuteron and the HD + molecule ion
The mass of the deuteron is said to be 0,1 billionth of a percent less than the value stored in specialist literature! More than 100 years after the discovery of the atomic nucleus, it is still unclear how heavy individual specimens are. The research team led by Sascha Rau from the Max Planck Institute for Nuclear Physics in Heidelberg succeeded in making an excellent “update”.
Source picture: Max Planck Institute for Nuclear Physics
The masses of the lightest atomic nuclei and the electron mass are linked, and their values influence observations in atomic physics, molecular physics and neutrino physics, as well as in metrology. The most accurate values for these fundamental parameters come from Penning Fallen mass spectrometry, which achieves relative mass uncertainties on the order of 10E (-11). However, redundancy checks using data from various experiments reveal significant inconsistencies in the masses of the proton, deuteron, and helion (the core of helium-3), suggesting that the uncertainty of these values may have been underestimated.
In the nature article (Vol 585 | 3 September 2020) the researchers present results from absolute mass measurements of the deuteron and the HD + molecule ion using 12C as a mass reference. Its value for the deuteron mass, 2,013553212535 (17) atomic mass units, has an accuracy that is 2,4 times better than the CODATA value and differs from it by 4,8 standard deviations. With a relative uncertainty of eight parts per trillion, this is the most precise mass value measured directly in atomic mass units. In addition, the measurement of the scientists, the determination of the mass of the HD + molecule ion, 3,021378241561 (61) atomic mass units, not only enables a strict consistency check of their results for the masses of the deuteron and the proton, but also provides an additional connection for the masses of tritium and helium-3 to the atomic mass unit. In combination with a recent measurement of the mass ratio of deuteron to proton, the uncertainty of the reference value of the proton mass can be reduced by a factor of three.
Read the full publication right here