Dissociation of molecules diatomic

The direct dissociation of diatomic molecules is the most well studied process in gas-surface dynamics, the one for which the combination of surface science and molecular beam teclmiques allied to the computation of total energies and detailed and painstaking solution of the molecular dynamics has been most successful. The result is a substantial body of knowledge concerning the importance of the various degrees of freedom (e.g. molecular rotation) to the reaction dynamics, the details of which are contained in a number of review articles [2, 36, 37, 38, 39, 40 and 41]. 

Darling G R and Holloway S 1995 Tlie dissociation of diatomic molecules Prog. Phys.. 58 1595... 

For both reactions studied, NO+CO and NO+propene, the effect of electrochemically pumped Na in increasing the extent of NO dissociation is large and significant. This is because unpromoted low index planes of Pt, Pt(lll), are relatively inert towards NO dissociation and we adscribe the NO dissociation as the key reaction-initiating step. Such dissociation of diatomic molecules in the field of coadsorbed cations has been discussed in detail by Lang et al [29], The rates of production of CO2. N2 and NjO all depend on... 

The experiments with a beam of silver particles were conducted at room temperature. The energy of dissociation of diatomic molecules of silver is 1.78 eV, the heat of evaporation of silver molecules is 95 kcal/mol [46], and the heat of evaporation of an uniatomic silver is 64 kcal/mol. Mass-spectrometric studies [46] of silver vapour above a metallic silver showed that the ratio of number densities of ions Ag /Ag2 is equal to two. In other studies [47], a considerably larger value of this ratio was found. At 1037 - 1147 C molecular mass of silver particles in vapours was found to be 278 90 [46], i.e., an average number of atoms in a molecule of silver is 2.56. 

Another typical class of examples is given by the dissociation of diatomic molecules as already alluded to above in the case of the H2 molecule where the correct dissociation behavior was only achieved by allowing for symmetry broken spin densities. This problem... 

Photochemical dissociation of diatomic molecules may occur either (a) by absorption in a spectral region showing a continuum or (b) by absorption in a region with bands which have more or less discrete appearance followed by crossover from one upper electronic state to another, which results in dissociation. The latter phenomenon is called predissociation and has been discussed at some length. 

We leave this discussion of differences in behavior of atoms in different electronic states with the statement that such work should be continued, particularly when it may apply to atoms formed by the primary photochemical dissociation of diatomic molecules. 

The one-dimensional potential curves depicted in Figures 1.1-1.3 represent the dissociation of diatomic molecules for which the potential V(Rab) depends only on the internuclear distance between atoms A and B. However, if one or both constituents are molecules, V is a multidimensional object, a so-called potential energy surface which depends on several (at least three) nuclear coordinates denoted by the vector Q = (Ql,Q2,Q3,---) (Margenau and Kestner 1969 Balint-Kurti 1974 Kuntz 1976 Schaefer III 1979 Kuntz 1979 Truhlar 1981 Salem 1982 Murrell et al. 1984 Hirst 1985 Levine and Bernstein 1987 ch.4 Hirst 1990 ch.3). The intramolecular and intermolecular forces, defined by... 

Alkali-metals are frequently used in heterogeneous catalysis to modify adsorption of diatomic molecules over transition metals through the alteration of relative surface coverages and dissociation probabilities of these molecules.21 Alkali-metals are electropositive promoters for red-ox reactions they are electron donors due to the presence of a weakly bonded s electron, and thus they enhance the chemisorption of electron acceptor adsorbates and weaken chemisorption of electron donor adsorbates.22 The effect of alkali-metal promotion over transition metal surfaces was observed as the facilitation of dissociation of diatomic molecules, originating from alkali mediated electron enrichment of the metal phase and increased basic strength of the surface.23 The increased electron density on the transition metal results in enhanced back-donation of electrons from Pd-3d orbitals to the antibonding jr-molecular orbitals of adsorbed CO, and this effect has been observed as a downward shift in the IR spectra of CO adsorbed on Na-promoted Pd catalysts.24 Alkali-metal-promotion has previously been applied to a number of supported transition metal systems, and it was observed to facilitate the weakening of C-0 and N-0 bonds, upon the chemisorption of these diatomic molecules over alkali-metal promoted surfaces.25,26... 

We will see in due course that there are important correlation rules between atomic term symbols and molecular electronic states, rules that are important in understanding both the formation and dissociation of diatomic molecules. Elementary accounts of the theory of atomic structure are to be found in books by Softley [3] and Richards and Scott [4], Among the more comprehensive descriptions of the quantum mechanical aspects, that by Pauling and Wilson [5] remains as good as any whilst group theoretical aspects are described by Judd [6],... 

We have described the orbital approaches to the electron configurations of diatomic molecules, both the molecular orbital and the united atom models. We now turn to the question of what types of molecular states result from given states of the separate atoms. If Russell Saunders coupling is valid for the separate atoms, the correlation rules, due to Wigner and Witmer [16] provide a valid and complete summary of the molecular states. This information is extremely important for an understanding of both the formation and dissociation of diatomic molecules. 

Liu W-K, Wu B, Yuan J-M. Nonlinear dynamics of chirped pulse excitation and dissociation of diatomic molecules. Phys Rev Lett 1995 75 1292-1295. 

Class IV . The first reactant is at a three-fold hollow site and the second is at a next nearest neighbour bridge site. Indeed, this represents a very common structure for a transition state on a (111) metal surface. Transition states with this structure are often observed in the dissociation of diatomic molecules - reactions which are the reverse of those currently under discussion. DFT calculations have shown that the dissociation of N2, CO, and on a variety of transition metal surfaces all proceed via this... 

Dissociation of diatomic molecules (and halogens in particular) in shock waves has been extensively studied. ° ° A lingering intriguing problem has been the unexpectedly low Arrhenius activation energy of such processes.Among the factors that have been considered as contributing to the observed kinetic behavior have been the enhancement of the rate of collisional dissociation by internal excitation of the diatomic molecules and the possible role of multiquantum transitions in which the molecule gains several vibrational quanta per collision.107... 

Pressure eflFects are observed on the dissociation of diatomic molecules and small polyatomic species such as CHO and HNO since the decomposition occurs in a bimolecular process. In reaction (7)... 

E.E.Nikitin, On a perturbation of the thermal equilibrium in thermal dissociation of diatomic molecules, Zhum.Fiz.Khim. 33, 519 (1959)... 

A.I.Maergoiz, E.E.Nikitin and L.Yu.Rusin, Dynamics of ion formation in collision-induced dissociation of diatomic molecules, in Khimiya Plasiiiy 11, ed. B. M. Smirnov, Moscow, Atomizdat, 1985, p. 3... 

High yields of gaseous hydrocarbons from H2 + CO have now been shown to occur in low-frequency [50 Hz. (8) and 60 Hz. (24)] discharges between electrodes, and electrodeless radiofrequency (2-110 MHz.) (6) and microwave (2450 MHz.) discharges. However, in all of these cases, the reaction does not appear to be an extremely rapid one, such as is the case for dissociation of diatomic molecules in a discharge, for instance. 

These anomalies may be restricted to radical reactions, but until they are resolved, they will inject considerable uncertainty into the utilization of shock tube data. A parallel, but not necessarily related anomaly, of shock tube data comes from studies of the dissociation of diatomic molecules behind incident shocks. Although the data can be... 

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