Electronic spectroscopy of organic acid dimers

The LN electronic spectroscopy of acetic, propionic, butyric, isobutyric ac id, and their dimers is studied by measurements of the temperature and pres sure dependence of their absorption spectra near 205 nm. The binding energy of each dimer is calculated using theoretical methods. The photo-absorptio n cross-sections for the monomer and dimer of each acid are calculated from 195-220 nm. The dimers are found to have a larger cross-section than the m onomers and a peak absorbance that is shifted to higher energy. Theory and experiment are used to compare the strength of the hydrogen bonds in the gr ound and excited state of these dimers. (C) 2001 Published by Elsevier Scie nce B.V.