Electronic Structures of the Methyl Radical: Effect of 3s Atomic Orbital of Carbon

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Abstract
By taking the 3s orbital of carbon into account, the self‐consistent‐field (SCF) LCAO—MO method has been applied to the ground state of the methyl radical. The 3s AO used has been determined for the valence state V4(1s22s2pπ+2pπ—3s) by a variational procedure, so that the orbital exponent of the 3s simple Slater AO obtained is 0.6374 instead of Slater's value 0.4833. For the other states with 3s AO, it is similarly concluded that good approximate 3s orbitals cannot be obtained by using Slater's rule, and more satisfactory shielding constants for the extra‐valence‐shell electron are given. Interactions between all electrons have been taken into consideration but the orthogonality relationship between 1s orbitals of carbon and hydrogen has been assumed. For the MOs occupied in the ground state, the forms are hardly changed by the inclusion of the 3s AO, and the contribution of the 3s AO is very small. For the lowest vacant orbital, however, this contribution is exceedingly great and qualitatively the conventional approximation by the 3s AO is rather more satisfactory than the use of the antibonding LCAO—MO constructed by the valence‐shell orbitals. In the lower electronic states calculated, such properties are prominent and the agreements with the observations are relatively good, especially by the inclusion of the 3s AO. The influence of the other extra‐valence‐shell orbitals is discussed.

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