The first excited triplet states of the nucleotide bases calculated with different semiempirical SCF schemes

Abstract

AbstractsThe n-electron distributions, spin densities, and energies of the first triplets of the nucleotide bases, uracil, thymine, cytosine, adenine, and guanine, were investigated in various semiempirical approximations. Results are presented for calculations using the semiempirical form of the closed-shell SCF configuration interaction method, of the different orbitals for different spins (unrestricted Hartree-Fock) treatment, with and without spin projection, and of the Roothaan's open-shell procedure.On a ttudit les distributions des Clectrons T, les densites de spin, et les energies des premiers triplets des bases nuclkotides (uracile, thymine, cytosine, adCnine, et guanine), dans le cadre des approximations semi-empiriques difftrentes : la forme semi-empirique de la mtthode SCF-CI pour des couches completes, la mtthode "different orbitals for different spins" (mtthode Hartree-Fock sans restrictions) avec et sans projection de spin et la mtthode de Roothaan pour des couches incompletes.Es wurden n-Elektronenverteilungen, Spindichten, und Energien der ersten Tripletten der Nukleotidbasen (Uracil, Thymin, Cytosin, Adenin und Guanin) mit verschiedenen semi-empirischen Approximationen berechnet : die semi-empirische Form der SCF-CIMethode fur abgeschlossene Schalen, die Methode "different orbitals for different spins" mit und ohne Spin-projektion, und die Roothaansche Methode fur offene Schalen.

THE OPTICAL PROPERTIES OF ADENINE FROM 1.8 TO 80 eV*

“…Studies such as these can be compared only indirectly with our transition energies since the absorption coefficient is a function of both l and cz through the relation Previous comparisons with our k values have been reported (Juan, 1975). Many attempts have been made to calculate energy states and hence, the absorption spectra of the purine bases (Bailey, 1970;Berthod et al, 1966Berthod et al, , 1967Callis, 1983;Clementi et al, 1969;Danilov et al, 1980;Fischer-Hjalmars and Nag-Chaudhuri, 1969;Giessner-Prettre and Pullman, 1968;Hug and Tinoco, 1973;Ito and I'Haya, 1976;Kuprievich, 1967;Mely and Pullman, 1969;Packer et al, 1969;Pullman et al, 1968;Savin et al, 1979;Srivastava and Mishra, 1980;Tanaka and Nagakura, 1966). These calculations present formidable problems and, at their present state of development, represent relatively crude approximations.…”