The bchaviour of n-electron SC wavefunctions and energy 1~~9s reproducing directly obtained bond orders is studied for diffcrcnt cxcitcd states of tram-butadicnc-1.3. In the development of methods for the direct calculation of bond orders [1,2] the question was raised as to what should be the wavefunctions of excited states of trans.butadiene-I ,3 reproducing the C&Ulatcd bond orders, obtained by attaining se[f-consistency i-or each state. In this note we analyst this problem by calculating the SC LCAO n-orbit& of trambutadiene by a PPP-type calculation. Excited states of butadiene have been discussed by Lefebvre [3] and by Nesbet [4], f 0 11 owing the classical treatment of ground-state butadicnc by Parr and MuUiken [5]
. The latter authors firstly raised the question of the validity of calculating excited states from "frozen" groundstate orbitnls. We would like to focus the attention in the behaviour of SC orbitals and eigenvalues of fransbutadiene obtained when self-consistency is performed for each state, that is, when "thawing" is allowed.
This question has become pressing after it was found that a fixed sequence of eigenvalues does not obtain in some molecules during electron excitations and ionization processes (6-91. * On leave of absence from thr: Conscjo Naciond de lnvestigaciones Cicntificas y Tccnicas (Argentina). Present address: Dtipnrtmnento de Fish. Facultnd de Ciencias ikactns. C..C. No 67, La Plats, Argentina.