Helion (chemistry)

A helion (symbol h) is the nucleus of a helium atom, a doubly positively charged cation. The term helion is a portmanteau of helium and ion, and in practice refers specifically to the nucleus of the helium-3 isotope, consisting of two protons and one neutron. The nucleus of the other (and far more common) stable isotope of helium, helium-4, consisting of two protons and two neutrons, is called an alpha particle or an alpha for short.

This particle is the daughter product in the beta-minus decay of tritium, an isotope of hydrogen:

3
1H
→ 3
2He1+
 		+ 
e−
 		+ 
ν
e

CODATA reports the mass of a helion particle as mh = 5.0064127862(16)×10−27 kg[1] = 3.014932246932(74) Da.[2]

Helions are intermediate products in the proton–proton chain reaction in stellar fusion.

An antihelion is the antiparticle of a helion, consisting of two antiprotons and an antineutron.

References
  1. "2022 CODATA Value: helion mass". The NIST Reference on Constants, Units, and Uncertainty. NIST. May 2024. Retrieved 2024-05-18.
  2. "2022 CODATA Value: helion mass in u". The NIST Reference on Constants, Units, and Uncertainty. NIST. May 2024. Retrieved 2024-05-18.


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