TEMPERATURE-DEPENDENCE STUDIES AND MODEL-CALCULATIONS OF NU(OH) AND NU(OD) BAND SHAPES OF SALICYLALDEHYDE

IR spectra of salicylaldehyde (OH and OD) have been studied over a wid e temperature range in the vapor phase, liquid Xe solution and Ar matr ices. Far IR and Raman spectra have been obtained. Ab initio calculati ons at the 3-21G* level have been performed in order to establish the geometry of the molecule, normal coordinates and frequencies of vibra tions. It has been found that profiles of both nu(OH) and nu(OD) bands are formed by the fundamental transition nu(s), by the weak sum trans ition nu(s) + nu(3), where nu(3) = 264 cm(-1) is an in-plane vibration involving deformation of the chelate ring with significant stretching of the intramolecular H-bond, and by a series of hot transitions from levels of nu(3) and other low frequency modes (nu(i)) of the chelate ring. The nu(OH) profile is perturbed additionally by several Fermi re sonances with overtones and combinations of bending vibrations delta(O H). Anharmonicity constants, which characterize coupling of nu(s) with nu(i) and delta(OH), have been derived from the temperature dependenc e of the first spectral moments of the bands, using the results of the 3-21G* treatment. Model calculations of nu(OH) and nu(OD) band shape s have been performed.