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Born-Oppenheimer breakdown

In the light of the accumulated evidence, it appears quite likely that the scattering of nitric oxide from metals does induce electronic transitions which represents a fundamental breakdown of the Born-Oppenheimer approximation. Clearly this falls in the category of electronically nonadi-abatic phenomena that we set out to understand. But there is a broader question. Is the Born-Oppenheimer breakdown significant within a broader chemical context ... [Pg.390]

Experimental probes of Born-Oppenheimer breakdown under conditions where large amplitude vibrational motion can occur are now becoming available. One approach to this problem is to compare theoretical predictions and experimental observations for reactive properties that are sensitive to the Born-Oppenheimer potential energy surface. Particularly useful for this endeavor are recombinative desorption and Eley-Rideal reactions. In both cases, gas-phase reaction products may be probed by modern state-specific detection methods, providing detailed characterization of the product reaction dynamics. Theoretical predictions based on Born-Oppenheimer potential energy surfaces should be capable of reproducing experiment. Observed deviations between experiment and theory may be attributed to Born-Oppenheimer breakdown. [Pg.392]

In the previous sections we have studied Born-Oppenheimer-breakdown corrections to two molecular properties, the rotational g tensor and the nuclear spin-rotation constant, i.e. the effect of the coupling between nuclear and electronic motion on the electronic energies. In this and the following sections we will now turn our attention to the effect of this coupling on the motion of the nuclei and will discuss Born-Oppenheimer-breakdown corrections to the rotational and vibrational energies. For the sake of a simpler presentation we will illustrate it for a diatomic molecule AB, where there is only one vibrational mode that involves changes in the internuclear... [Pg.141]

How important the breakdown of the Born-Oppenheimer approximation is in limiting our ability to carry out ab initio simulations of chemical reactivity at metal surfaces is the central topic of this review. Stated more provocatively, do we have the correct theoretical picture of heterogeneous catalysis. This review will restrict itself to a consideration of experiments that have begun to shed light on this important question. The reader is directed to other recent review articles, where aspects of this field of research not mentioned in this article are more fully addressed.10-16... [Pg.386]

Perhaps the first evidence for the breakdown of the Born-Oppenheimer approximation for adsorbates at metal surfaces arose from the study of infrared reflection-absorption line-widths of adsorbates on metals, a topic that has been reviewed by Hoffmann.17 In the simplest case, one considers the mechanism of vibrational relaxation operative for a diatomic molecule that has absorbed an infrared photon exciting it to its first vibrationally-excited state. Although the interpretation of spectral line-broadening experiments is always fraught with problems associated with distinguishing... [Pg.386]

Hence, according to the symmetry selection rule, n —> n transitions are allowed but n —> ti transitions are forbidden. However, in practice the n —> it transition is weakly allowed due to coupling of vibrational and electronic motions in the molecule (vibronic coupling). Vibronic coupling is a result of the breakdown of the Born-Oppenheimer approximation. [Pg.43]

Understand that intermolecular radiationless transitions of excited states are caused by a breakdown of the Born-Oppenheimer approximation. [Pg.77]

The electronic contributions to the g factors arise in second-order perturbation theory from the perturbation of the electronic motion by the vibrational or rotational motion of the nuclei [19,26]. This non-adiabatic coupling of nuclear and electronic motion, which exemplifies a breakdown of the Born-Oppenheimer approximation, leads to a mixing of the electronic ground state with excited electronic states of appropriate symmetry. The electronic contribution to the vibrational g factor of a diatomic molecule is then given as a sum-over-excited-states expression... [Pg.322]

All of the calculations have been performed at the experimental equilibrium distance R = 1.128 A, in order to enable a proper comparison with the EOM-CCSD reference. In so far as there are neither largely interacting excited states nor special reasons for expecting a breakdown of the Born Oppenheimer approximation, great changes in the MAE are not expected if one takes the (SC) SDCI ground state equilibrium value for Re which is Re = 1.140 A (very close to the CCSD value, as expected Cfr. table 1). We have performed a separate calculation of the whole set of VEE with the aug-cc-pVDZ basis set at the Rg distance, in any case. The results have not been included in table II for the sake of clarity, but the total MAE values where 2.34 eV for the MR-SDCI and 0.17 eV for (SC)2mR-SDCI. [Pg.93]

We have now stated the central theme of this review. Several sections to follow are devoted to detailing the nature of our statement, and several sections to describing variations on the theme. Specifically, Section II describes the fundamental quantum mechanics of compound states, Section III contains a brief survey of the experimental data and theoretical background relevant to this review, and Section IV outlines the nature of the Born-Oppenheimer (BO) approximation and its breakdown in cases of interest. In Section V we consider the nature of the eigenstates of large molecules and the implications of the breakdown of the BO approximation. This leads us to discuss, in Section VI, a simple model of the time evolution of the states of large molecules and an interpretation of the... [Pg.151]

Breakdown of the Born-Oppenheimer Approximation. The B-O approximation is based on the independence of the motions of nuclei and electrons. This is generally a reasonable assumption, except at the crossing point of two electronic states where a minor nuclear displacement is linked to the transition between two electronic states (Figure 3.31). [Pg.60]


See other pages where Born-Oppenheimer breakdown is mentioned: [Pg.383]    [Pg.383]    [Pg.386]    [Pg.391]    [Pg.392]    [Pg.285]    [Pg.737]    [Pg.234]    [Pg.128]    [Pg.130]    [Pg.137]    [Pg.144]    [Pg.383]    [Pg.383]    [Pg.386]    [Pg.391]    [Pg.392]    [Pg.285]    [Pg.737]    [Pg.234]    [Pg.128]    [Pg.130]    [Pg.137]    [Pg.144]    [Pg.768]    [Pg.164]    [Pg.386]    [Pg.60]    [Pg.585]    [Pg.78]    [Pg.51]    [Pg.75]    [Pg.87]    [Pg.471]    [Pg.129]    [Pg.149]    [Pg.184]    [Pg.187]    [Pg.192]    [Pg.198]    [Pg.255]    [Pg.95]    [Pg.69]    [Pg.355]    [Pg.432]    [Pg.542]    [Pg.108]    [Pg.219]   
See also in sourсe #XX -- [ Pg.386 , Pg.390 , Pg.391 ]

See also in sourсe #XX -- [ Pg.346 , Pg.357 ]

See also in sourсe #XX -- [ Pg.346 , Pg.357 ]

See also in sourсe #XX -- [ Pg.17 , Pg.27 ]




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