Theoretical study of the electronic spectrum of diimide by AB initio methods
1975; Elsevier BV; Volume: 7; Issue: 2 Linguagem: Inglês
10.1016/0301-0104(75)87002-9
ISSN1873-4421
AutoresKrishnaswamy Vasudevan, Sigrid D. Peyerimhoff, Robert J. Buenker, W.E. Kammer, Hsiang-lin Hsu,
Tópico(s)Atomic and Molecular Physics
ResumoA series of ab initio calculations is reported for the ground and low-lying valence and Rydberg states of diimide N2H2. Symmetric bending potential curves for both the cis and trans forms of this system have been obtained at the SCF level of treatment. In addition Cl calculations have been carried out for the trans-diimide ground state equilibrium nuclear conformation, using a configuration selection procedure described elsewhere; an associated energy extrapolation scheme is also employed which enables the effective solution of secular equations with orders of up to 40000. The ensuing Cl wavefunctions are interpreted in the discussion and the corresponding calculated energy differences between the various electronic states are compared with experimental transition energy results for both diimide and for related systems such as trans-azomethane. A more detailed analysis of the observed absorption bands in the 1Bg-X1Ag transition in N2H2 is also given, making use of calculated potential curve data as well as the pertinent Cl vertical energy difference. The dipole-forbiddenness of the excitation process is thereupon concluded to result in a distinct non-verticality for this electronic band system, causing its absorption maximum to occur at a position some 0.6 eV to the blue of the so-called vertical transition, i.e., that for which maximum vibrational overlap is obtained.
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