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Excited States And Photochemistry Of Saturated Molecules. 11. Potential Energy Surfaces In Low-Lying States Of Ethane, James W. Caldwell, Mark S. Gordon
Excited States And Photochemistry Of Saturated Molecules. 11. Potential Energy Surfaces In Low-Lying States Of Ethane, James W. Caldwell, Mark S. Gordon
Mark S. Gordon
Ab initio calculations at both the restricted Hartree-Fock (RHF) and singly excited configuration interaction (SEC I) levels have been carried out on sections of the potential energy surfaces for a number of low-lying excited singlet electronic states of ethane. All vertical states below the first ionization potential are predominantly Rydberg in character, as are all minima detected on the potential energy surfaces. The lowest 1Eg state is predicted to have only a very small (""" 1 kcal/mol) barrier separating its minimum-energy structure from the 1A" ethylidene + 1 ~/ H2 products. Since the vertical Eg molecule has more than enough …
Gas-Phase Photolysis Of 2,2-Dimethylbutane, 2,2,3-Trimethylbutane, 2,2,3-Trimethyl-2-Silabutane, And 2,2,3,3-Tetramethyl-2-Silabutane At 147 Nm, Daryl J. Doyle, S. K. Tokach, Mark S. Gordon, Robert D. Koob
Gas-Phase Photolysis Of 2,2-Dimethylbutane, 2,2,3-Trimethylbutane, 2,2,3-Trimethyl-2-Silabutane, And 2,2,3,3-Tetramethyl-2-Silabutane At 147 Nm, Daryl J. Doyle, S. K. Tokach, Mark S. Gordon, Robert D. Koob
Mark S. Gordon
The 147-nm photolyses of 2,2-dimethylbutane, 2,2,3-trimethylbutane, 2,2,3-trimethyl-2-silabutane (isopropyltrimethylsilane), and 2,2,3,3-tetramethyl-2-silabutane (tert-butyltrimethylsilane) are reported. In addition, the mercury-sensitized photolyses of i-C4H10, trimethylsilane, and mixtures of i-C4H10 and trimethylsilane are reported which give disproportionation to combination (D/C) ratios of 2.1 ::1::0.2 and 0.28::1::0.05 for (CH3) 3C + (CH3) 3C and (CH3)gSi + (CH3)gSi, respectively, and D/C ratios of 1.86::1:: 0.15 and 0.55 ::1:: 0.08 for (CH3)gC + (CH3)aSi to form 2-methyl-2-silapropene and i-C4H8, respectively. With the completion of this work, several trends and generalizations can be drawn concerning the importance of various processes in linear vs. branched alkanes and alkylsilanes. These conclusions …
Effects Of Polar Substituents On Carbon-Silicon Multiple Bonds, Mark S. Gordon
Effects Of Polar Substituents On Carbon-Silicon Multiple Bonds, Mark S. Gordon
Mark S. Gordon
The results of ab initio calculations on the effects of fluorine and lithium substitution on silaethyne and silaethylene and their isomers are presented. It is found that fluorine has a strong stabilizing effect when attached to silicon. This results in the predictions (a) that a distorted 1-fluoro-1-silaethyne is the most stable structure of HCSiF and (b) that 1,1-difluoro- 1-silaethylene is much lower in energy than 1,2-difluoromethylsilylene. Approximate correlation corrections are added to study the HC~iF - FHC=Si and HC==SiLi - LiHC=Si potential energy surfaces.
Excited States And Photochemistry Of Saturated Molecules. X. Ab Initio Calculations On The Vertical States Of Methylsilane, Mark S. Gordon
Excited States And Photochemistry Of Saturated Molecules. X. Ab Initio Calculations On The Vertical States Of Methylsilane, Mark S. Gordon
Mark S. Gordon
The vertical excitation energies are investigated for singlet and triplet states of methylsilane. To analyze the importance of Rydberg functions and of both valence and Rydbergd functions, a sequence of ten different basis sets are considered in conjuction with a single excitation configuration interaction. It is found that all of the singlet states below the first ionization potential may be characterized as Rydberg states, while there is considerable valence character in some of the low‐lying triplets. If the valence s and p functions are represented reasonably well (e.g., with a split valence basis set), the role of valence d orbitals …
Self‐Consistent Molecular Orbital Methods. Xxiii. A Polarization‐Type Basis Set For Second‐Row Elements, Michelle M. Franci, William J. Pietro, Warren J. Hehre, J. Stephen Binkley, Mark S. Gordon, Douglas J. Defrees, John A. Pople
Self‐Consistent Molecular Orbital Methods. Xxiii. A Polarization‐Type Basis Set For Second‐Row Elements, Michelle M. Franci, William J. Pietro, Warren J. Hehre, J. Stephen Binkley, Mark S. Gordon, Douglas J. Defrees, John A. Pople
Mark S. Gordon
The 6‐31G* and 6‐31G** basis sets previously introduced for first‐row atoms have been extended through the second‐row of the periodic table. Equilibrium geometries for one‐heavy‐atom hydrides calculated for the two‐basis sets and using Hartree–Fock wave functions are in good agreement both with each other and with the experimental data. HF/6‐31G* structures, obtained for two‐heavy‐atom hydrides and for a variety of hypervalent second‐row molecules, are also in excellent accord with experimental equilibrium geometries. No large deviations between calculated and experimental single bond lengths have been noted, in contrast to previous work on analogous first‐row compounds, where limiting Hartree–Fock distances were in …