论文信息 - Electron diffraction studies of hot molecules. IV. Asymmetries of nonbonded distribution functions of SF6, SiF4, and CF4

Electron diffraction studies of hot molecules. IV. Asymmetries of nonbonded distribution functions of SF6, SiF4, and CF4

Highly significant improvements in the agreement between observed and calculated intensities of electrons diffracted by hot molecules were obtained by optimizing the skew parameter a for the nonbonded distributions. Derived a values (±2σ) were 2.75(11), 0.72(13), and 2.0(4) A−1 for SF6, SiF4, and CF4, respectively. These measured skew parameters are approximately 2 A−1 higher in each case than values previously proposed on the basis of Morse asymmetry factors and the nonlinear transformation between curvilinear and normal coordinates of molecules. The principal factor responsible for the increase is the previously unknown intrinsic anharmonicity in bending deformations. Silicon tetrafluoride has a lower a value than the other molecules studied primarily because its bending force constant is lower, relative to stretching. Practical as well as theoretical implications of present findings are discussed.

J. Stanton | L. Bartell

[1] W. Vance,et al. Electron diffraction studies of hot molecules. III. Stretching and bending anharmonicity in CF3Cl , 1984 .

[2] L. Bartell. Effects of anharmonicity of molecular vibrations on the diffraction of electrons. Part V. Tetrahedral molecules , 1984 .

[3] L. Bartell. Effects of anharmonicity of molecular vibrations on the diffraction of electrons : Part IV. "Anharmonic shrinkage" , 1982 .

[4] L. Bartell,et al. Electron diffraction studies of hot molecules. I. Observed and calculated thermal expansions of SF6, CF4, and SiF4 , 1982 .

[5] L. Bartell,et al. Electron diffraction studies of hot molecules. II. ‘‘Anharmonic shrinkage effects’’ in SF6, CF4, and SiF4 , 1982 .

[6] R. Hilderbrandt,et al. A variational treatment of the effects of vibrational anharmonicity on gas-phase electron diffraction intensities: Part II. Temperature dependence , 1981 .

[7] L. Bartell. Effects of anharmonicity of molecular vibrations on the diffraction of electrons: Part III. Predictive models , 1980 .

[8] L. Bartell,et al. Electron Diffraction Study of Rhenium Fluorides. II. Structure, Pseudorotation, and Anharmonic Coupling of Modes in ReF7 , 1970 .

[9] S. J. Cyvin. Molecular Vibrations and Mean Square Amplitudes , 1968 .

[10] K. Kuchitsu. Effect of Molecular Vibrations on Gas Electron Diffraction. I. Probability Distribution Function and Molecular Intensity for Diatomic Molecules , 1967 .