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Expansion Approach To Photodissociation Dynamics. I. Theory, Kazuo Takatsuka, Mark S. Gordon Jan 1981

Expansion Approach To Photodissociation Dynamics. I. Theory, Kazuo Takatsuka, Mark S. Gordon

Mark S. Gordon

We propose a new formulation for a photodissociation process to which an expansional (or algebraic) quantum‐variation‐method of scattering is applicable. By solving a ’’full collision’’ problem which describes a multichannel process on the repulsive surface, the photodissociation scheme takes account of interchannel coupling from the outset. Our expression for the amplitude of the partial linewidth is similar to that of the ’’half‐collision’’ approximation of Jortner e t a l. The present formalism differs in that the scattering wave functions take acount of interchannel coupling exactly. As a result, only on‐the‐energy‐shell contributions appear in the partial linewidth.

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Expansion Approach To Photodissociation Dynamics. Ii. Correction Formula For Linewidth And Numerical Examples For Hcn, Kazuo Takatsuka, Mark S. Gordon Jan 1981

Expansion Approach To Photodissociation Dynamics. Ii. Correction Formula For Linewidth And Numerical Examples For Hcn, Kazuo Takatsuka, Mark S. Gordon

Mark S. Gordon

A correction formula for energy disposal and linewidth of photodissociation dynamics is proposed. This formula was derived from an identity similar to the Kato identity of the scattering theory. Thanks to the correction formula the resultant linewidth turns out to be more accurate and stable even when a relatively poor basis set is used. Numerical examples for assumed direct dissociation of HCN, DCN, and TCN and for the predissociation of HCN and DCN are presented.

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Ring Strain In Cyclopropane, Cyclopropene, Silacyclopropane, And Silacyclopropene, Mark S. Gordon Dec 1980

Ring Strain In Cyclopropane, Cyclopropene, Silacyclopropane, And Silacyclopropene, Mark S. Gordon

Mark S. Gordon

The strain energy in four three-membered rings is calculated by using the appropriate isodesmic reactions. Calculations with and without d functions on the heavy atoms indicate that while these polarization functions tend to reduce ring strain, the addition of d orbitals has little effect on the predicted trends. While introduciton of unsaturation drastically increases the strain in the carbon system (cyclopropane---. cyclopropene), this is not the case for silicon (silacyclopropane--+ silacyclopropene). As a result cyclopropane and cyclopropene are predicted to be the least and most strained rings, respectively.

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Synthesis Of Peroxyacetyl And Peroxyaroyl Nitrates. Complexation Of Perqxyacetyl Nitrate With Benzene, Tina M. Kravetz, Steve W. Martin, G. David Mendenhall Oct 1980

Synthesis Of Peroxyacetyl And Peroxyaroyl Nitrates. Complexation Of Perqxyacetyl Nitrate With Benzene, Tina M. Kravetz, Steve W. Martin, G. David Mendenhall

Steve W. Martin

Convenient procedures are given for the condensed-phase synthesis Of peroxyacetyl nitrate (PAN), peroxybenzoyl ni- sponding peracid% sulfuric acid, and sodium nitrate- The compounds of considerable interest because of their physio- logical and action in polluted atmospheres (1-4). Samples of such compounds are routinely needed for cali- several syntheses have been published (I, 5-8). The procedure of Louw et al. (5) is particularly convenient because the re- corrosive reagents are required. trate, and m-chloroperoxybenzoyl nitrate from the corre- position of the ‘H NMR signal from peroxyacetyl nitrate in CC14-benzene mixtures depended on the solvent composition benzene, with K,, = 0.095 at …

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The Effects On Grain-Boundary Processes Of The Steps In The Boundary Plane Associated With The Cores Of Grain-Boundary Dislocations, Alexander H. King, D. A. Smith Jan 1980

The Effects On Grain-Boundary Processes Of The Steps In The Boundary Plane Associated With The Cores Of Grain-Boundary Dislocations, Alexander H. King, D. A. Smith

Alexander H. King

The contribution of the associated steps to the properties of grain-boundary dislocations are investigated. Two methods of step-height determination are given and it is shown that the step height, like the Burgers vector, must be conserved during the reactions of grain-boundary dislocations: this is not always automatic and additional coherent steps must take part in some reactions. The energies associated with steps have been estimated and compared with the elastic energies of grain-boundary dislocations; these comparisons suggest that (a) the reduction of elastic energy alone may not be a sufficient criterion for the progress of a reaction and (b) that …

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Excited States And Photochemistry Of Saturated Molecules. Vii. Potential Energy Surfaces In Excited Singlet States Of Methane, Mark S. Gordon, James W. Caldwell Jan 1979

Excited States And Photochemistry Of Saturated Molecules. Vii. Potential Energy Surfaces In Excited Singlet States Of Methane, Mark S. Gordon, James W. Caldwell

Mark S. Gordon

Potential energy surfaces are investigated for a number of low‐lying excited singlet states of methane, using a split valence plus Rydberg basis set and singly excited CI. Of the six minima found, the lowest two are valence states. The lowest minimum corresponds to the products 1 1 B 1 CH2+1 1Σ g + H2, in agreement with the observed threshold photochemistry, and is accessible by five separate routes from the lowest vertical state. The second valence minimum is a square planar structure. Of the four Rydberg minima detected, one is a local minimum on the otherwise dissociative B 1surface and …

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Second-Row Molecular Orbital Calculations. 5. A Minimal Basis Indo For Sodium-Chlorine, Mark S. Gordon, Mark D. Bjorke, Fred J. Marsh, Michael S. Korth Apr 1978

Second-Row Molecular Orbital Calculations. 5. A Minimal Basis Indo For Sodium-Chlorine, Mark S. Gordon, Mark D. Bjorke, Fred J. Marsh, Michael S. Korth

Mark S. Gordon

An INDO method is developed for molecules containing Na-CJ. Using only valences and p orbitals, the parametrization is carried out in the spirit of the approach originally taken by Pople and co-workers. The reliability of the method is tested by calculating geometries, dipole moments, and internal rotation barriers for approximately 100 molecules. The improvement in predictive ability relative to previous parametrizations is considerable. Predicted geometries are nearly as good as those for ST03G. Dipole moments of molecules containing Si and Clare in excellent agreement with experiment, while for P and S the agreement is only fair.

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Excited States And Photochemistry Of Saturated Molecules. Ix. Vertical Excited States Of Silane, Mark S. Gordon Jan 1978

Excited States And Photochemistry Of Saturated Molecules. Ix. Vertical Excited States Of Silane, Mark S. Gordon

Mark S. Gordon

The vertical excited states of silane are investigated using ten different basis sets to systematically compare the effects of (a) Rydberg functions, (b) diffuse d functions, (c) valence d functions, and (d) a split valence shell. Wavefunctions are generated using all singly excited configurations, excluding inner shells. The low‐lying singlet states are dominated by excitations into the diffuse orbitals, while low‐lying triplets have significant valence character. Valence d functions have a minor effect on excitation energies if an adequate valence s p basis set is used. The main effect of Rydbergd functions is to introduce additional Rydberg states below the …

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An Electrochemical Investigation Of The Effects Of Antiaromaticity And Determination Of The Increased Antiaromatic Destabilization Of Cyclobutenedione Upon Reduction, Reuben D. Rieke, C. Kenneth White, Lee D. Rhyne, Mark S. Gordon, John F. W. Mcomie, Niegel P. Hacker Aug 1977

An Electrochemical Investigation Of The Effects Of Antiaromaticity And Determination Of The Increased Antiaromatic Destabilization Of Cyclobutenedione Upon Reduction, Reuben D. Rieke, C. Kenneth White, Lee D. Rhyne, Mark S. Gordon, John F. W. Mcomie, Niegel P. Hacker

Mark S. Gordon

Electrochemical studies were carried out on a series of cyclic 1,2-diones under nonaqueous conditions. From thereduction potentials and Hucke! molecular orbital calculations, the increase in antiaromatic destabilization of cyclobutenedione upon reduction is estimated to be at least 14 kcal/mol. The EPR spectrum of the radical anion of naphtho[b ]cyclobutadienoquinone is presented. Also, INDO calculations were carried out on several of the diones and the results are consistent with the experimental observations.

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Excited States And Photochemistry Of Saturated Molecules. I. General Approach And Application To Propane, Patrick M. Saatzer, Robert D. Koob, Mark S. Gordon Sep 1975

Excited States And Photochemistry Of Saturated Molecules. I. General Approach And Application To Propane, Patrick M. Saatzer, Robert D. Koob, Mark S. Gordon

Mark S. Gordon

Following Ruedenberg, we suggest that a useful measure of chemical binding is the two-center, one-electron interference contribution to the energy in the electronic state of interest. Using this conceptual framework, the vertical valence excited states of propane in the optimal ground state geometry are examined using INDO in its original parametrization. The results are compared with available experimental information. The calculations yield bond energies which are consistent with observed decomposition modes for ground states of small alkanes and excited states of propane. Configuration interaction calculations are discussed in the case of propane. Inclusion of all single excitations from the ground …

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Localized Orbital Studies Of Hydrogen Bonding. Ii. Dimers Containing H 2 0, Nh 3, Hf, H 2 Co, And Hcn, Mark S. Gordon, Dennis E. Tallman, Cathy Monroe, Michael Steinbach, Jill Armbrust Mar 1975

Localized Orbital Studies Of Hydrogen Bonding. Ii. Dimers Containing H 2 0, Nh 3, Hf, H 2 Co, And Hcn, Mark S. Gordon, Dennis E. Tallman, Cathy Monroe, Michael Steinbach, Jill Armbrust

Mark S. Gordon

INDO localized molecular orbitals (LMO's) are utilized for investigating the nature of intermolecular hydrogen bonding in the fully geometry optimized dimers (HFh, (Hz0)2, (NH3)2, FH-OH2, HOH-FH, FH-NH3, H 2NH-FH, H20-HNH2, HOH-NH3, HCN-HF, and HzCO-HF. The results suggest that a reasonable measure of relative hydrogen bond strengths should be the intra bond, two-center, one-electron interference energy connecting the acceptor atom and donated proton. This approach views the net stabilization energy of a hydrogen bonded dimer as arising from a large energy decrease due to formation of the hydrogen bond, modified by smaller energy increases due to internal decreases in monomer bond …

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Second Row Molecular Orbital Calculations. Geometries, Internal Rotation Barriers, And Dipole Moments Of Methylsilane, Disilane, Methyl Mercaptan, And Methyl Phosphine, Mark S. Gordon, Loren Neubauer Sep 1974

Second Row Molecular Orbital Calculations. Geometries, Internal Rotation Barriers, And Dipole Moments Of Methylsilane, Disilane, Methyl Mercaptan, And Methyl Phosphine, Mark S. Gordon, Loren Neubauer

Mark S. Gordon

The internal rotation barriers of methylsilane, methyl mercaptan, methylphosphine, and disilane are calculated with and without complete geometry optimization in three different CNDO parametrizations. It is found that Santry's recent reparametrization is most reliable for both geometries and barriers and that geminal and bonded interference interactions are more important than those between vicinal atoms for these molecules. None of the parametrizations give reasonable dipole moments.

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An Indo Investigation Of The Structure And Bonding Of Acetylacetone And Trifluoroacetylacetone, Mark S. Gordon, Robert D. Koob Sep 1973

An Indo Investigation Of The Structure And Bonding Of Acetylacetone And Trifluoroacetylacetone, Mark S. Gordon, Robert D. Koob

Mark S. Gordon

The energies of the enol forms of acetylacetone (ACAC) and trifluoroacetylacetone (TFA) have been minimized with respect to all structural parameters using the INDO molecular orbital theory. The internal hydrogen for enol ACAC is found to be symmetrically arranged between the two oxygens with an OHO angle of 152 o and an OH bond length of 1.174 A. Fluorine substitution to produce the electronically asymmetric molecule TFA causes only a slight asymmetry in the position of the internally bonded hydrogen. In both molecules this hydrogen is located in a well-defined single potential energy minimum. Electron density is increased on the …

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Molecular Orbital Study Of Internal Rotation, Mark S. Gordon Jun 1969

Molecular Orbital Study Of Internal Rotation, Mark S. Gordon

Mark S. Gordon

The CND0/2 molecular orbital method is used to predict and explain the barriers to internal rotation in a number of molecules. The observed 3: 2: 1 ratio of the barriers in ethane, methylamine, and methyl alcohol is approximately reproduced as are most trends in the barriers of fluoro-substituted propenes; however, the calculated trends for fluoro-substituted ethanes are incorrect. The barriers in H202, F202, N2H4, N2F4, and NH20H and the effect of geometry optimization on these barriers are also discussed. The major source of the barriers in the first group of molecules is predicted to be due primarily to nonbonded interactions …

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A Molecular Orbital Study Of The Isomerization Mechanism Of Diazacumulenes, Mark S. Gordon, Herbert Fischer May 1968

A Molecular Orbital Study Of The Isomerization Mechanism Of Diazacumulenes, Mark S. Gordon, Herbert Fischer

Mark S. Gordon

Inversion barriers and geometries of AB3 molecules calculated using the INDO method3 are in satisfactory agreement with experiment. The diazacumulenes (11) with an even number of atoms are calculated to have a higher configurational stability than those with an odd number of atoms. cis-Diimide and cis-difluorodiimide should be more stable thermodynamically than the corresponding trans isomers. The configurational stability of carbodiimide is predicted to be low (comparable to that of ammonia), the isomerization being a combination of rotation and inversion, However, difluorocarbodiimide should be stable enough to permit resolution.

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Approximate Self‐Consistent Molecular‐Orbital Theory. Vi. Indo Calculated Equilibrium Geometries, Mark S. Gordon, J. A. Pople Jan 1968

Approximate Self‐Consistent Molecular‐Orbital Theory. Vi. Indo Calculated Equilibrium Geometries, Mark S. Gordon, J. A. Pople

Mark S. Gordon

The INDO (intermediate neglect of differential overlap) self-consistent theory has been used to calculate equilibrium geometries for a series of small polyatomic molecules with one or two polyvalent atoms (carbon, nitrogen, or oxygen). The results are compared with experimental data where available.

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Molecular Orbital Theory Of The Electronic Structure Of Organic Compounds. I. Substituent Effects And Dipole Moments, J. A. Pople, Mark S. Gordon Aug 1967

Molecular Orbital Theory Of The Electronic Structure Of Organic Compounds. I. Substituent Effects And Dipole Moments, J. A. Pople, Mark S. Gordon

Mark S. Gordon

A recent approximate self-consistent molecular orbital theory (complete neglect of differential overlap or CNDO) is used to calculate charge distributions and electronic dipole moments of a series of simple organic molecules. The nuclear coordinates are chosen to correspond to a standard geometrical model. The calculated dipole moments are in reasonable agreement with experimental values in most cases and reproduce many of the observed trends. The associated charge distributions of dipolar molecules show widespread alternation of polarity in both saturated and unsaturated systems. These results suggest that charge alternation may be an intrinsic property of all inductive and mesomeric electronic displacements.

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