Accurate ab initio potential energy surface and spectral calculation for the HOCO+ + H2O reaction

• We calculated the reaction between HOCO+ and H2O using ab initio theory.
• The results show several different products of the HOCO+ + H2O reaction.
• We calculated spectrums of the ground states and excited states for the product.
• Some reaction products are candidates for the unverified spectral lines.

The reaction between HOCO+ and H2O has been examined using ab initio theory to locate and optimize the critical points on the potential energy surfaces. The results show that there are several product channels. First, the ion H3O+, which has been observed in the interstellar medium, can be generated by direct abstraction of H from HOCO+. Second, the HOCO+ cation can combine with a water molecule to generate the new molecule, HOC(OH)2+, for which stable structures have been found. Third, a transition state can exist where the reaction proceeds through HOC(O)OH2+ radicals to produce the products HCOOH+ + OH. We have also calculated structural parameters, energies, and vibrational frequencies of both the HOC(O)OH2+ adduct and the products which are presented to help in their future identification. Using the calculated spectrums of the ground states and excited states we have proposed possible structures which correspond to observed spectral lines.