Abstract: The equilibrium structures, frequencies and energies of HONO2 ,HNO3＋ , HOONO conformers and HOONO＋conformers are calculated in detail by density function theory(DFT) at B3LYP theory level with 6-311G(d) basis set. The calculated results indicate that HOONO and HOONO＋ both have three stable conformers, and HOONO has three structures with imaginary frequencies. Additionally, the potential energy curves of rotation of O－O bond of HOONO and HOONO＋ are calculated and used to discuss the geometry change between different conformers. The active vibrational modes in the photoelectron spectra (PES) of HONO2 and HOONO conformers are predicted based on our calculated equilibrium structures and vibrational frequencies.

Key words: Equilibrium structures, Conformers, Photo Electron Spectroscopy, 　HONO₂, HOONO, Theoretical calculation