A structural model for associated liquid ethanol developed from transient spectroscopy

We propose a detailed structural model for ethanol oligomers assuming it to form open chains. An inhomogeneous broadening with a width of about 100 cm(-1) of the OH-stretching mode of the hydrogen-bonded species is considered, a parabolic increase of the absorption strength and a cubic dependency of the frequency of this vibration with position within the-associate. With these asumptions we are able to account for the measured conventional IR absorption spectra of ethanol at different dilutions in CCl4 with the most probable length of the associates ranging between 2 and 13 molecules, respectively. Application of our model to time-resolved spectroscopy on a 0.17 M sample with excitation performed at 3340 cm(-1) yields a length of the excited oligomers of 4 to 5 and of broken species of 2 to 3, respectively. (C) 1997 American Institute of Physics. [S0021-9606(97)52047-2].