Vibrational energy distribution

A simple phase space model can be used to compute the CO product vibrational energy distribution as a function of the available energy,12-14 Eav. The maximum energy which can be partitioned among the products degrees of freedom is the reaction exoergicity, Ex = hv-DH°[(CO)5W-CO]. For a 351 nm photolysis,... 

Figure 2. Vibrational energy distribution of the CO product formed via the 351 nm photolysis of W(CO)s. Experimental data are indicated asfl. The lines correspond to results obtained by phase space calculations with an available energy of 40 and 35 Kcal/mole.

Conclusions. Time-resolved CO laser absorption spectroscopy can provide information useful in characterizing the primary photochemical channels in gas-phase transition metal carbonyls. We have found that product vibrational energy distributions indicate that W(CO)g and Cr(CO>6 dissociate via different... 

We have also investigated the application of Franck-Condon models in fitting the CO product vibrational energy distribution and find they are unable to do so. D. Anderson, J. Brown, R. Fletcher, K. Prather and R. Rosenfeld, manuscript in preparation. 

Rotational-vibrational energy distribution function I 10-3 erg-sec Nuclear spin quantum number... 

Shapiro, M. and Bersohn, R. (1980). Vibrational energy distribution of the CH3 radical photo dissociated from CH3I, J. Chem. Phys. 73, 3810-3817. 

The separation into a vibrational and an electronic part is implied by the Placzek polarizability theory. The further analysis of vibrational motions has in the past typically been accomplished by calculating the vibrational energy distribution in valence coordinates. For the large-scale skeletal motions often important in ROA, and for relating Raman and ROA scattering cross-sections to the vibrational motions of structural parts of an entity, a different approach is needed. 

Figure 2 shows the results of two typical experiments. The observed CO vibrational energy distribution produced from the reactions 0(3P) + C2H2 and... 

Figure 2. Vibrational energy distributions of the CO formed in 0(3P) + CtHt (O) and Of3P) + CtH,CsH reactions (-----------), are statistically prodicted distribu-...

For the determination of product vibrational and rotational distributions, we must consider the time for vibrational or rotational relaxation by gas-phase collisions. This is not as strongly dependent on the nature of the products as it is for electronic quenching. Rotational relaxation is a much more efficient process than vibrational relaxation, requiring typically less than one hundred collisions to rotationally relax a molecule compared with several thousand collisions to bring about vibrational relaxation [76]. Thus, primary product vibrational energy distributions may be determined at pressures greater than 10-4 Torr, whilst much lower pressures are required to observe unrelaxed rotational state distributions. 

The effect of reagent vibrational excitation on the detailed form of the product vibrational energy distributions has been studied [200—202] for the reactions... 

Initial analyses of the product vibrational energy distributions for X + HX suggested that they could be described by a linear surprisal plot. However, more recent work [545] suggests that there is a deviation... 

Consequently B (or possibly A) rebounds and interacts again with C. These secondary encounters may be of two types either the interaction is of a repulsive kind, in which case C may abstract energy from AB broadening the vibrational energy distribution as it departs [267] or A and C may interact attractively (for example, if B and C are the same), and AC may become the molecular product rather than AB. The probability of secondary encounters will be greatest when AB is ionic or has a small reduced mass, since then the vibrational amplitude will be large the effect will be less likely where the reduced mass of the products is small. 

---