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 ab out 100 cm(-1) of the OH-stretching mode of the hydrogen-bonded specie s is considered, a parabolic increase of the absorption strength and a cubic dependency of the frequency of this vibration with position wit hin the-associate. With these asumptions we are able to account for th e measured conventional IR absorption spectra of ethanol at different dilutions in CCl4 with the most probable length of the associates rang ing between 2 and 13 molecules, respectively. Application of our model to time-resolved spectroscopy on a 0.17 M sample with excitation perf ormed 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 Ins titute of Physics. [S0021-9606(97)52047-2].