State torsional

Etor state Torsional potential energy local Hamiltonian Magnetic field strength at nucleus of a... 

The changes which occur in thermosetting resins undergoing cure have been studied by a variety of techniques. Supported sample methods have been used to monitor the relative changes modulus and damping behavior from the initial low viscosity liquid to the fully cured rubbery or glassy state. Torsional braid analysis (TBA) employs a resin sample impregnated on a... 

Figure 10. Ground- and excited-state torsional potentials of AA. In addition to the ordinary LE state, a new low-lying excited state with partial CT character exists in the vicinity of the LE state.

Figure 7.10 Expanded view of adiabatic B-state torsional potential in the region of the torsional crossing of tIq -radical (circles, solid hne) and Uq -radical (squares, dotted line) species (cf Figure 7.9). The crossing occurs at — -152.23087 a.u. and...

In earlier studies the gradient thresholds for CAS geometry convergence were often weaker than those used here, and accurate analytic frequencies were unavailable to detect false (transition state) stationary points. The slight effects of B-state torsional deformation (if present at lower CAS levels) may therefore have fallen within the numerical uncertainties. 

Small ground-state torsions around a double bond may result in the carbon atoms of the double bond undergoing a modest rehybridization. The resultant incorporation of partial s-character into lobes of the bond effects better ji overlap. There is little torsional strain in the double bond of cyclohexene, but it is postulated that reaction pathways leading to trans- or cis-addition may exhibit a transition-state differential of several kcalmol from this source. 

Figure A3.13.15. Master equation model for IVR in highly excited The left-hand side shows the quantum levels of the reactive CC oscillator. The right-hand side shows the levels with a high density of states from the remaining 17 vibrational (and torsional) degrees of freedom (from [38]).

The first study in which a full CASSCE treatment was used for the non-adiabatic dynamics of a polyatomic system was a study on a model of the retinal chromophore [86]. The cis-trans photoisomerization of retinal is the primary event in vision, but despite much study the mechanism for this process is still unclear. The minimal model for retinal is l-cis-CjH NHj, which had been studied in an earlier quantum chemisti7 study [230]. There, it had been established that a conical intersection exists between the Si and So states with the cis-trans defining torsion angle at approximately a = 80° (cis is at 0°). Two... 

Conformational free energy simulations are being widely used in modeling of complex molecular systems [1]. Recent examples of applications include study of torsions in n-butane [2] and peptide sidechains [3, 4], as well as aggregation of methane [5] and a helix bundle protein in water [6]. Calculating free energy differences between molecular states is valuable because they are observable thermodynamic quantities, related to equilibrium constants and... 

Rather than calculate the etithaltty conti ibutioti of the torsional states individually, an empirical sum that is an integral multiple of 0.42 kcal mol per torsional degree of freedom is assigned to flexible molecules in MM3, Torsional motion of a methyl gntup is iK)t added k) a calculated because it is included in the... 

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