Excitation product internal

The instrumentation described in the foregoing sections is all based On mass analysis of the charged or neutral products of ion-neutral interactions. A different type of apparatus, which has been extensively utilized to characterize internally excited products from ion-neutral processes, is that in which an optical detector is employed to observe radiative emissions... 

Internally excited products from interactions of atomic ions with tri-... 

The second approach to the study of reactive scattering involves the use of some spectroscopic method for the detection of the products in specified internal quantum states. Molecular spectroscopy is well suited to the determination of the relative populations in individual states since the quantum numbers of the upper and lower states of a molecular line in an assigned transition are known. Moreover, the intensities may be directly related to concentrations of specific internal states. The original implementation of this approach for the study of reactive scattering involved observation of spontaneous infrared emission from the radiative decay of vibrationally excited products [4, 5]. This approach is still being employed, however now usually with detection of the emission with Fourier transform [6], rather than grating-tuned spectrometers. In some cases, emission from electronically excited products can be observed for highly exothermic reactions. 

This striking contrast in decomposition behavior between the products from recoil F substitution and alkyl replacement reactions is intriguing, but its dynamical basis remains uncertain. Cold"" alkyl replacement products could conceivably result from either of the follovsdng extreme mechanisms (i) 3-center direct reactions in which product internal excitation is confined to the newly formed bond or (ii) dynamically more complex processes that are Golden Rule forbidden (57,79,80) at large collision energies. The further study of this question r resents a fertile area for future research. 

Here M is any component of the reaction mixture that stabilizes vibra-tionally excited products on one or more collisions. Thermodynamic energy limits for each process were estabhshed. Thus, the integral of the CF4 excitation function could be estimated and used to obtain the initial internal energy distribution of the CFa F formed in Equation 1. The qualitative features of both results (5,21) are the same, and, as expected, the total energy deposited by hot fluorine atoms (22) is somewhat greater than by hot tritium in these replacement reactions. 

For a simple treatment of the (RS) perturbation expansions, it is often desirable to have just one wave operator 2, which is defined on the whole model space. This desire requests however that the distinction of internal and external excitations must apply for all determinants < ) e A4 in the same way [43]. This can be seen, for instance, from the second term (on the rhs) of the Bloch Eq. (16) which contains the operator product PVS2P. The projector P, standing left of this product, eliminates all contributions of the operator which leads out of the model space. For a single wave operator, acting on the whole model space, this projection must be the same for all determinants < ) e M. We therefore find that an unique dispartment of the excitations into internal and external ones is a necessary and sufficient condition. The importance of the proper choice of the model space and their classification has been discussed in detail by Lindgren [43]. 

To make quantitative statements about the product internal distribution a computer program is utilized to simulate the observed excitation spectrum [10]. As input for the calculations we estimate the relative vibrational and rotational populations. Each line is weighted by the population of the initial (v, J ) level, by the Franck-Condon factor and the rotational line strength of the pump transition. At each frequency, the program convolutes the lines with the laser bandwidth and power to produce a simulated spectrum such spectra are compared visually with the observed spectra and new estimates are made for the (v ,J") populations. Iteration of this process leads to the "best fit" as shown in the lower part of Fig. 3. For this calculated spectrum all vibrational states v" = 0...35 are equally populated as is shown in the insertion. The rotation, on the other hand, is described by a Boltzmann distribution with a "temperature" of 1200 K. With such low rotational energy no band heads are formed for v" < 5 in the Av = 0 sequence and for nearly all v" in the Av = +1 sequence (near 5550 A). 

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