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:^{[citation needed]}

³
₁H

→

³
₂He

+

e⁻

+

ν
_e

CODATA reports the mass of a helion particle as m_h = 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

^ "2022 CODATA Value: helion mass". The NIST Reference on Constants, Units, and Uncertainty. NIST. May 2024. Retrieved 2024-05-18.
^ "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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[physconst-mh-1] "2022 CODATA Value: helion mass". The NIST Reference on Constants, Units, and Uncertainty. NIST. May 2024. Retrieved 2024-05-18.

[physconst-mhDa-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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[2]