Potential energy constant

VIBRATIONAL SPECTRA, POTENTIAL ENERGY CONSTANTS, MEAN AMPLITUDES OF VIBRATIONS AND CALCULATED THERMODYNAMIC PROPERTIES OF ACETAMIDE. 

B-H bond. Other calculations of the force constants and potential-energy constants have been made (197, 316), but they all need to be repeated with the improved vibrational assignments and molecular parameters referred to earlier. Mean-square vibrational amplitudes have been studied (13, 60, 315), those for the bridge hydrogen atoms exceeding those for the terminal atoms. 

The Frr, etc., arc appropriate linear combinations of the potential energy constants in terms of the valence coordinates and at. 

Here / and /" are the strain constants which occur since the four XY stretches ( ) arc not independent of the six YY stretches (90). In using this type of potential function, it is necessary eventually to eliminate the redundant coordinates, of which there are seven in the present example. Moreover, the redundancy conditions must be obtained to the second order to permit proper accounting for the linear potential energy constants f and f. When this is done, the potential energy may ultimately be written in the form... 

Weissman H. B., Meister A. G., Cleveland F. E. Infrared spectral data and assignments for CHCI2F and CHCIF2 and potential energy constants and calculated thermodynamic properties.—J. Chem. Phys., 1958, v. 29, 72—77. 

Additionally, the ionic character of the BC bond has been estimated to be about 20 to 30% (210) from the observed quadrupole coupling constant of B (205). Infrared (200, 211-214) and Raman spectra (211, 215, 216) results for BH3CO are in essential agreement with the assigned structure. Using available spectroscopic data, potential energy constants, rotational distortion constants, and thermodynamic properties have been calculated for BH3CO (211, 213, 217-219). 

To define the rotation-vibration constants in terms of more fundamental parameters or to understand the origin of various nonrigidity effects in the rotational spectrum, the general rotation-vibration Hamiltonian must be employed. This Hamiltonian contains pure rotation and vibration terms as well as interaction terms between rotation and vibration. Perturbation treatments to various orders are required to characterize the different rotation-vibration effects. Space does not permit further discussion of this however, we mention that such a perturbation treatment shows that the a constants depend on the cubic potential energy constants of the molecule. 

Because of the general difficulty encountered in generating reliable potentials energy surfaces and estimating reasonable friction kernels, it still remains an open question whether by analysis of experimental rate constants one can decide whether non-Markovian bath effects or other influences cause a particular solvent or pressure dependence of reaction rate coefficients in condensed phase. From that point of view, a purely... 

The bulk of the infomiation about anhannonicity has come from classical mechanical calculations. As described above, the aidiannonic RRKM rate constant for an analytic potential energy fiinction may be detemiined from either equation (A3.12.4) [13] or equation (A3.12.24) [46] by sampling a microcanonical ensemble. This rate constant and the one calculated from the hamionic frequencies for the analytic potential give the aidiannonic correctiony j ( , J) in equation (A3.12.41). The transition state s aidiannonic classical sum of states is found from the phase space integral... 

In particular, the probability of finding the unimolecular reactant within its potential energy well decreases according to this law. Thus F detemrines tire lifetune of the state and the state specific unimolecular rate constant is... 

The fitting parameters in the transfomi method are properties related to the two potential energy surfaces that define die electronic resonance. These curves are obtained when the two hypersurfaces are cut along theyth nomial mode coordinate. In order of increasing theoretical sophistication these properties are (i) the relative position of their minima (often called the displacement parameters), (ii) the force constant of the vibration (its frequency), (iii) nuclear coordinate dependence of the electronic transition moment and (iv) the issue of mode mixing upon excitation—known as the Duschinsky effect—requiring a multidimensional approach. 

There are other important properties tliat can be measured from microwave and radiofrequency spectra of complexes. In particular, tire dipole moments and nuclear quadmpole coupling constants of complexes may contain useful infonnation on tire stmcture or potential energy surface. This is most easily seen in tire case of tire dipole moment. The dipole moment of tire complex is a vector, which may have components along all tire principal inertial axes. 

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