Can someone tell me what the HD+ ion is?

[AxiomOfChoice]

I know $H_2^+$ is a bound state of an electron and two protons, but what's $\text{HD}^+$? Is the D just a stand-in for an arbitrary nucleus that may, or may not, be a proton?

I found the following website with information about this cation that leads me to believe that the "D" is not just a stand-in, since $\text{HD}^+$ seems to have a well defined molecular weight: http://webbook.nist.gov/cgi/cbook.cgi?ID=C12181167&Units=SI&Mask=1000#Diatomic

 

[Borek]

D stands for deuterium (hydrogen isotope).

 

[AxiomOfChoice]

Nice; thanks. So $\text{HD}^+$ consists of a bound state of a proton, a deuteron (one proton, one neutron), and an electron?

 

[Borek]

Yes. It is just like H₂⁺ - ionized hydrogen molecule - just with one hydrogen replaced by deuterium.