  The sheer interstellar abundance of helium makes any bound molecules or
complexes containing it of potential interest for astrophysical observation.
This work utilizes high-level and trusted quantum chemical techniques to
predict the rotational, vibrational, and rovibrational traits of HeHHe+,
HeHNe+, and HeHAr+. The first two are shown to be strongly bound, while HeHAr+
is shown to be more of a van der Waals complex of argonium with a helium atom.
In any case, the formation of HeHHe+ through reactions of HeH+ with HeH3+ is
exothermic. HeHHe+ exhibits the quintessentially bright proton-shuttle motion
present in all proton-bound complexes in the 7.4 micron range making it a
possible target for telescopic observation at the mid-IR/far-IR crossover point
and a possible tracer for the as-of-yet unobserved helium hydride cation.
Furthermore, a similar mode in HeHNe+ can be observed to the blue of this close
to 6.9 microns. The brightest mode of HeHAr+ is dimmed due the reduced
interaction of the helium atom with the central proton, but this fundamental
frequency can be found slightly to the red of the Ar-H stretch in the
astrophysically detected argonium cation.
