THE ROVIBRATIONAL SPECTRUM OF HYDROXYLAMINE - A COMBINED HIGH-RESOLUTION EXPERIMENTAL AND THEORETICAL-STUDY

This paper reports the rovibrational spectrum of hydroxylamine (NH,OH) recorded by interferometric Fourier transform spectroscopy with a res olution of up to 0.004 cm(-1) close to the Doppler limit at room tempe rature, from 800 cm(-1) up to the visible range of the spectrum. Detai led rotational analyses for 32 bands include all nine fundamentals and numerous overtones up to 10 500 cm(-1). Approximate absolute band str engths, band centers and vibrational assignments are presented for a t otal of 72 bands up to the 4v(1) OH stretching overtone. The spectra a re interpreted in terms of multidimensional vibrational calculations w ith potential and dipole surfaces constructed by multidimensional spli ne interpolation from more than 2x10(5) ab initio MP2/6-31G* points. The full three dimensional treatment of the torsion-inversion problem reveals well separated time scales for the two processes with a cis po tential, well supporting localized wave functions for the zero point a nd fundamental levels. Up to five dimensional normal coordinate models are employed for the analysis and dynamic interpretation of the compl ete vibrational spectrum up to 21 000 cm(-1). Good quantitative agreem ent between observed spectra and results from ab initio calculations i s obtained with a simple harmonic scaling procedure without any furthe r empirical refinement. The comparison of various coupling schemes rev eals an efficient path for the coupling between the OH and NH2 manifol ds mediated through the OH bending mode. The implications for the effe ctive homogeneous broadening at high energies are discussed. (C) 1997 American Institute of Physics.