Molecular potential energy curve

Morgan J D III and Simon B 1980 Behavior of molecular potential energy curves for large nuclear separations/nf. J. Quantum Chem. 17 1143... 

Sketch the qualitative molecular potential energy curves for the N—N bond on one graph for N2H4, N2, and N,. ... 

Once the mechanisms of dynamic processes are understood, it becomes possible to think about controlling them so that we can make desirable processes to occur more efficiently. Especially when we use a laser field, nonadiabatic transitions are induced among the so-called dressed states and we can control the transitions among them by appropriately designing the laser parameters [33 1]. The dressed states mean molecular potential energy curves shifted up or down by the amount of photon energy. Even the ordinary type of photoexcitation can be... 

Fig. 3.2 A schematic of a molecular potential energy curve with three stationary points two local minima (32 E/dq2 > 0) and one transition state (32 E/dq2 < 0).

The activated complex is located at the intersection of the two curves. However, the noncrossing rule states that molecular potential energy curves of states of the same symmetry do not cross but instead split into an upper and a lower curve. The noncrossing rule implies that if the reactants in their ground states... 

Rice, O.K., Predissociation and the crossing of molecular potential energy curves, J. Chem. Phys., 1, 375, 1933. 

An interpretation in terms of molecular potential—energy curves was advanced almost simultaneously by Horiuti and Polanyi and by Bell, " the two treatments corresponding respectively to a covalent and an ionic formulation. The former is probably closer to reality, and will be followed here. 

There is a fair match between the harmonic oscillator potential and the real molecular potential energy curve we saw in Chapter 5 at low potential energy (this is our requirement that R should be near R in the Taylor series). The match becomes worse as we go up in energy and the potential becomes anharmonic. At low vibrational energy, the harmonic oscillator is a good approximation to most molecular vibrations. 

Use Figure 14.29 to comment on the variances between a Morse oscillator and a true molecular potential energy curve. 

Fig. 12.14 A molecular potential energy curve can be approximated by a parabola near the bottom of the well.

Fig. 12.18 The vibrational energy levels associated with the general shape of a molecular potential energy curve are less widely spaced at high excitation.

Figure 9-1. The molecular potential energy curve of a diatomic molecule is shown. The minimum point in the curve represents the equilibrium geometry (i.e. equilibrium bond length) of the molecule.

A transition structure is the molecular species that corresponds to the top of the potential energy curve in a simple, one-dimensional, reaction coordinate diagram. The energy of this species is needed in order to determine the energy barrier to reaction and thus the reaction rate. A general rule of thumb is that reactions with a barrier of 21 kcal/mol or less will proceed readily at room temperature. The geometry of a transition structure is also an important piece of information for describing the reaction mechanism. 

If the system can only be modeled feasibly by molecular mechanics, use the potential energy curve-crossing technique or a force held with transition-structure atom types. 

Recently, we have developed a full theoretical treatment of electron capture processes involving an ab initio molecular calculation of the potential energy curves and of the radial and rotational couplings followed, according to the collision energy range concerned, by a semi-classical [21-23] orquantal [24] collision treatment. 

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