Multireference singles and doubles configuration interaction study of the photoelectron spectrum of HOminus;2

摘要

Multireference singles and doubles configuration interaction (MRDhyphen;CI) electronic structure calculations are carried out on the hydroperoxyl radical and its negative ion. Potential energy curves of the ground state of the anion and of the ground and first excited states of the neutral molecule along the Ondash;OH coordinate are employed to compute the Franckndash;Condon factors for the electron photodetachment processes HO2(Xthinsp;2Alsquo;,Athinsp;2Arsquo;)+elarr;HOminus;2(Xthinsp;1Arsquo;). The theoretical spectrum agrees fairly well with the photoelectron spectrum reported by Oakes, Harding, and Ellison, and is consistent with their assignment of the peaks K and D as origins for the electron loss transitions to the HO2AandXstates, respectively. An alternative choice of peak E asXlarr;Xminus;origin yields better agreement between computed and experimental Franckndash;Condon factors than does the peak D assignment, but is less satisfactory when energetic considerations are taken into account. Two independentabinitioresults lend support to the value of 1.078plusmn;0.017 eV for the measured adiabatic electron affinity of HO2, which is in good agreement with the best value inferred from the MRDhyphen;CI calculations of 1.069plusmn;0.05 eV. The matter is not settled, however, as some inconsistencies in the experimental data still cast some doubts on the assignment of the peaks and the accuracy of the HO2EA.