ConstantID

Helion relative atomic mass

Atomic & nuclearMeasured

Ar(h) = 3.014 932 246 932(74)

Value
3.014 932 246 932
Standard uncertainty
7.4 × 10−11
Relative uncertainty
2.5 × 10−11 (25 parts per trillion)
Status
Measured
Symbol
Ar(h)
Source
CODATA 2022 via NIST · NIST entry

Use in a calculation

# helion relative atomic mass, CODATA 2022 (NIST)
helion_relative_atomic_mass = 3.014932246932  # standard uncertainty 7.4e-11

# SciPy: scipy.constants.physical_constants['helion relative atomic mass']

What it is

The mass of the helion, the nucleus of helium-3 (two protons and one neutron), divided by the atomic mass constant (one twelfth of the mass of a carbon-12 atom). It has no unit.

How the value changed, 1998–2022

Each point is one CODATA adjustment, plotted as its difference from the 2022 value; the bars show one standard uncertainty (an arrowhead means the bar runs off the chart).

helion relative atomic mass: CODATA values 1998–2022 relative to the 2022 value, in parts per trillion, with one-standard-uncertainty bars−150−100−500+50+100+150parts per trillion1998200220062010201420182022

Relative uncertainty

helion relative atomic mass: relative standard uncertainty in each CODATA adjustment, logarithmic scale10⁻¹²10⁻¹¹10⁻¹⁰1998200220062010201420182022
CODATAValue (uncertainty)Relative uncertaintyChange from previous
20223.014 932 246 932(74)2.5 × 10−11 −2.5 σ of 2018
20183.014 932 247 175(97)3.2 × 10−11

“Change from previous” is the shift in the value divided by the standard uncertainty of the previous adjustment. Earlier values are converted into the current unit where NIST changed it (for example J s to J Hz⁻¹).

Related constants

Atomic & nuclear mh/me Helion-electron mass ratio 5495.885 279 84(16) Atomic & nuclear gh Helion g factor −4.255 250 6995(34) Atomic & nuclear μh Helion magnetic moment −1.074 617 551 98(93) × 10−26 J T−1 Atomic & nuclear μh/μB Helion magnetic moment to Bohr magneton ratio −1.158 740 980 83(94) × 10−3 Atomic & nuclear μh/μN Helion magnetic moment to nuclear magneton ratio −2.127 625 3498(17) Atomic & nuclear mh Helion mass 5.006 412 7862(16) × 10−27 kg Atomic & nuclear mhc2 Helion mass energy equivalent 4.499 539 4185(14) × 10−10 J Atomic & nuclear mhc2 Helion mass energy equivalent in MeV 2808.391 611 12(88) MeV