“…The vibrational spectra of unsubstituted polyenes and especially of buta-1,3-diene [1] and hexa-1,3,5-triene [2,3] have extensively been studied and normal coordinate analyses have been carried out by many authors which are cited and discussed in Refs. [4][5][6][7][8]. In the field of a, x-diphenylpolyenes the molecular structures of trans-stilbene (tSB) and cis-stilbene (cSB) in the gas phase have been studied theoretically [9][10][11][12] and by electron diffraction [13,14].…”