Anharmonic vibrational spectra of hydroxylamine and its 15N, 18O, and deuterium substituted analogs.
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.
Kowal
Andrzej T
AT
Institute of Inorganic Chemistry and Metallurgy of Rare Elements, Wrocław University of Technology, Poland. atk@ichn.ch.pwr.wroc.pl
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*
D009587:Nitrogen Isotopes; D010103:Oxygen Isotopes; D019811:Hydroxylamine; D003903:Deuterium