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SCF CI and SCF open‐shell studies of the base components of the nucleic acids
Author(s) -
Kuprievich V. A.
Publication year - 1967
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560010504
Subject(s) - singlet state , chemistry , excited state , thymine , cytosine , ionization energy , uracil , triplet state , atomic physics , guanine , open shell , ground state , ionization , computational chemistry , physics , dna , ion , nucleotide , biochemistry , organic chemistry , gene
The π‐electron structure of adenine, guanine, cytosine, thymine and uracil in their ground, ionized, singlet and triplet excited states are investigated by means of the SCF CI and SCF open‐shell methods. The calculations for singlets fit the maxima of the absorption bands well. The energy difference between the first and the second singlet states of adenine is found to be very small. The open‐shell method leads to the same relative ionization potential as does the SCF (with the integrals empirically corrected). The calculated energies of the triplet states almost coincide in the SCF open‐shell and the SCF CI approximation. The calculated transition energies to the first triplet state of the pyrimidines are higher than in the case of the purines. The value of the singlet–triplet separation energy of purines is in agreement with experimental data.