Rotational Analysis Of The High-Resolution Spectra For Water Cation And Hydroxyacetone

The water cation(H₂O⁺)is a very popular molecular ion in the nature.Its spectral data are of great importance in astrophysics and atmospheric chemistry.A large number of spectroscopic studies have been carried out in the far-infrared,mid-infrared, near-infrared,and visible region since 1970s.In this dissertation,about 1400 rotationally-resolved spectral lines of H₂O⁺ in which the ground state are concemed have been compiled from all the available experimental data,yielding 925 ground-state combination differences(GSCDs).These GSCDs were fitted with a weighted least-squares fitting program ASYTOP developed by T.Sears.A set of improved molecular constants,e.g.rotational,spin-rotation interaction and their centrifugal distortion constants,have been determined.Subsequently,the 925 GSCDs together with 210 far-infrared laser magnetic resonance transitions(from the literature)were used to perform a global analysis with the same program,and thirty-two molecular parameters were simultaneously determined,including g-factors and hyperfine structure constants.The high resolution spectrum of hydroxyacetone(CH₃COCH₂OH)is of great interest to both chemists and astrophysicists.Its spectrum is very complicated owing to the presence of an internal methyl group rotor,which has a very low barrier to internal rotation of about 65 cm^-1,and an intramolecular hydrogen bond.The high resolution infrared spectrum of the C-O stretching fundamental band of hydroxyacetone was recorded in supersonic jet expansion between 1103 and 1112 cm^-1for the first time by C.X.Duan and D.Luckhaus in 2004.However,these spectra have not been assigned.In this work,a preliminary analysis has been carried out using the WANG program based on the accurate spectroscopic parameters for the ground state determined by A.J.Apponi et al..A total of 277 transitions arising from A-species have been assigned and a set of precise molecular parameters for the vibrationally-excited state and the band origin have been determined.