  High-resolution mass spectra of helium droplets doped with gold and ionized
by electrons reveal He$_n$Au$^+$ cluster ions. Additional doping with heavy
noble gases results in NenAu+, Ar$_n$Au$^+$, Kr$_n$Au$^+$, and Xe$_n$Au$^+$
cluster ions. The high stability predicted for covalently bonded Ar$_2$Au$^+$,
Kr$_2$Au$^+$, and Xe$_2$Au$^+$ is reflected in their relatively high abundance.
Surprisingly, the abundance of Ne$_2$Au$^+$ which is predicted to have zero
covalent bonding character and no enhanced stability features a local maximum,
too. The predicted size and structure of complete solvation shells surrounding
ions with essentially non-directional bonding depends primarily on the ratio
$\sigma$* of the ion-ligand $versus$ the ligand-ligand distance. For Au$^+$
solvated in helium and neon the ratio $\sigma$* is slightly below 1, favoring
icosahedral packing in agreement with a maximum observed in the corresponding
abundance distributions at $n$ = 12. He$_n$Au$^+$ appears to adopt two
additional solvation shells of $I_h$ symmetry, containing 20 and 12 atoms,
respectively. For Ar$_n$Au$^+$, with $\sigma$* $\approx$ 0.67, one would expect
a solvation shell of octahedral symmetry, in agreement with an enhanced ion
abundance at $n$ = 6. Another anomaly in the ion abundance at Ar$_9$Au$^+$
matches a local maximum in its computed dissociation energy.
