AB-INITIO STUDY OF NITROXIDE, HNO-

The first ab initio theoretical study has been performed on the ground state of nitroxide, HNO-, in combination with a comparison study of t he ground state of two chemically similar systems, peroxy radical, HO2 , and the neutral nitroxyl radical, HNO. An optimum geometry and vibra tional frequencies are reported for all species, and results are compa red to experimental and theoretical values. A bent geometry is obtaine d for HNO-, with an equilibrium bond angle of 106.2-degrees, and bond lengths of R(NO) = 1.333 angstrom and R(NH) = 1.045 angstrom. The calc ulated fundamental vibrational frequencies (in cm-1) are: nu1 (N-H str etch), 3029; nu2 (bend), 1474; and nu3 (N-O stretch), 1183. The bendin g frequency and the N-O stretching frequency in the ion are similar to the bending frequency and the O-O stretching frequency of HO2, while the N-H stretching frequency of HNO- is similar to the N-H stretching frequency of HNO. In addition, the GAUSSIAN 1 and GAUSSIAN 2 methods a re used for the determination of an electron affinity for HNO. The cal culated electron affinity of 0.23 +/- 0.10 eV is in reasonable agreeme nt with the experimentally determined value of 0.338 +/- 0.015 eV.