title: Abundance and chemistry of interstellar HOCO+.
abstract: We derive HOCO+ column densities approximately 10(15) cm-2 toward the Galactic center and < or = 10(12) cm-2 for cold dark clouds from observations and an LVG model.  We mapped the HOCO+ 4(04)-3(03) line toward Sgr A.  The fractional abundance of HOCO+ in the Galactic center region is three orders of magnitude larger than predicted by quiescent ion-molecule chemistry and an order of magnitude larger than predicted by a MHD shock model.  If HOCO+ traces interstellar CO2, the implied high abundance ([CO2] approximately [CO]) in the Galactic center may result from UV photolysis of grain mantles.
authors.affiliation: Department of Physics and Astronomy, University of Massachusetts, Amherst 01003, USA.
authors.forename: Y C
authors.initials: YC
authors.lastname: Minh
authors.forename: M K
authors.initials: MK
authors.lastname: Brewer
authors.forename: W M
authors.initials: WM
authors.lastname: Irvine
authors.forename: P
authors.initials: P
authors.lastname: Friberg
authors.forename: L E
authors.initials: LE
authors.lastname: Johansson
mesh_terms: D055580:Astronomical Phenomena; D001256:Astronomy; D002245:Carbon Dioxide / Q000032:analysis* / Q000737:chemistry*; D005118:Extraterrestrial Environment; D008956:Models, Chemical; D011522:Protons; D016082:Solar System; D013696:Temperature
chemical_list: D011522:Protons; D002245:Carbon Dioxide