
%0 Journal Article
%A Beecham, AF 
%A Hurley, AC 
%A Johnson, CHJ 
%T Hydrogen bonding and the n &#8594; p* blue shift in a,b-unsaturated ketones. II. Franck-Condon factors and estimates of the effects of hydrogen bonding on CO bond lengths
%J Australian Journal of Chemistry
%D 1980/04/01
%V 33
%N 4
%P 699-705
%K 
%R https://doi.org/10.1071/CH9800699
%U https://www.publish.csiro.au/paper/CH9800699 
%X Vibrational wave functions and Franck-Condon factors are calculated for the n &#8594; &#960;* transition in &#945;,&#946;-unsaturated ketones by approximating vibrations of the chromophore by those of a diatomic moiety (CO). Comparison of the results with recent c.d. and u.v. absorption measurements indicates that the principal effect of hydrogen bonding on the n &#8594; &#960;* system of these ketones arises from a differential lengthening of the CO bond in the excited electronic state as compared with the ground electronic state. It is these bond length changes which cause (through the Franck-Condon factors) the redistribution of intensity between vibrational sub-bands which is such a striking feature of recent highly resolved c.d. spectra. 
