engleski

Theoretical modeling of the formic acid dimer infrared spectrum: Shaping the O-H stretch band

The potential energy surface of the formic acid dimer is investigated in the vicinity of the minima. The linear absorption spectrum in the region of the OH antisymmetric stretch is analized using the combination of a second-order perturbative treatment and non-perturbative calculations in reduced dimensionality. The importance of particular coupling mechanisms is studied systematically and it has been shown that the red-shift of the OH stretching (bu) center frequency is almost exclusively caused by the Davyidov coupling to the symmetric OH stretch vibration. We find that anharmonic coupling to low frequency dimer stretching and rocking modes and Fermi resonances to mid-infared modes contribute to the width, but only in a minor extent to the frequency of the OH stretching (bu) band maximum

infrared spectrum; formic acid dimer; OH stretch

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