title: Anharmonic vibrational spectra of hydroxylamine and its 15N, 18O, and deuterium substituted analogs.
abstract: Vibrational self-consistent field (VSCF) and correlation-corrected vibrational self-consistent field (CC-VSCF) methods were used to compute the anharmonic frequencies of fundamentals, overtones, and combination transitions of natural abundance hydroxylamine, 15NH2OH, NH2(18)OH, ND2OD, ND2OH, and NH2OD isotopomers at second order Møller-Plesset perturbation theory (MP2) in basis sets of triple-zeta quality. Frequencies of the fundamental transitions observed in the gas phase spectrum were reproduced by CC-VSCF treatment within 20 cm(-1) in TZV(d,p) and TZV(2d,2p) basis sets, and the change of basis set composition had only minor effect on the frequencies of the computed fundamentals. CC-VSCF computed wave numbers of overtone and combination transitions were typically within 1-40 cm(-1) of the gas phase band positions, except for those resulting from multiple excitations of v2, v3, and v7 fundamentals, because of a strong mutual coupling between these modes. Integral transition intensities calculated at MP2 level closely followed those of experimental spectrum, including intensity decrease in v1, 2v1, 3v1 progression, and 30-fold intensity increase of 2v8 in respect to that of v8 fundamental. The frequency of the OH torsional fundamental was found to be strongly dependent on the mode-mode interaction potential among v9 and v1, v7, v2, v4, v5 modes. Band shifts resulting from 15N, 18O and complete 2H substitutions were reproduced almost quantitatively by CC-VSCF computation in TZV(d,p) basis. Computed anharmonic isotope frequency shifts were different from those obtained in the harmonic approximation and no scaling procedure seemed capable of performing their interchange.
authors.affiliation: Institute of Inorganic Chemistry and Metallurgy of Rare Elements, Wrocław University of Technology, Poland. atk@ichn.ch.pwr.wroc.pl
authors.forename: Andrzej T
authors.initials: AT
authors.lastname: Kowal
mesh_terms: D055592:Biophysical Phenomena; D001703:Biophysics; D003903:Deuterium / Q000032:analysis*; D019811:Hydroxylamine / Q000737:chemistry; D009587:Nitrogen Isotopes / Q000032:analysis*; D010103:Oxygen Isotopes / Q000032:analysis*; D013053:Spectrophotometry / Q000379:methods*
chemical_list: D009587:Nitrogen Isotopes; D010103:Oxygen Isotopes; D019811:Hydroxylamine; D003903:Deuterium