title: HCNH+:  a new interstellar molecular ion.
abstract: A new molecular ion, HCNH+, or protonated HCN, has been detected in the interstellar medium.  The J = 1-0, 2-1, and 3-2 rotational transitions of this species have been observed toward Sgr B2.  Using a large velocity gradient model calculation, the column density of HCNH+ is found to be approximately 4 x 10(14) cm-2, about one order of magnitude less than that estimated for HCO+ and HCN in this source.  Such a column density implies a fractional abundance for HCNH+ in Sgr B2 of approximately 3 x 10(-10), one to several orders of magnitude greater than the values predicted by ion-molecule models of interstellar chemistry.  The high observed abundance of this species, relative to theoretical calculations, suggests that the destruction of HCNH+ by dissociative recombination is slower than expected, or that the formation rate of the ion has been underestimated.
authors.affiliation: Five College Radio Astronomy Observatory, University of Massachusetts, Amherst, USA.
authors.forename: L M
authors.initials: LM
authors.lastname: Ziurys
authors.forename: B E
authors.initials: BE
authors.lastname: Turner
mesh_terms: D055580:Astronomical Phenomena; D001256:Astronomy; D005118:Extraterrestrial Environment; D006856:Hydrogen Cyanide / Q000032:analysis / Q000737:chemistry*; D007477:Ions; D008872:Microwaves; D008962:Models, Theoretical; D011522:Protons; D013057:Spectrum Analysis
chemical_list: D007477:Ions; D011522:Protons; D006856:Hydrogen Cyanide