Products angular distribution spectroscopy

The photolysis of aromatic species with tetranitromethane in perfluoro alcohol solvent has been studied, in which the radical cations were observed by EPR spectroscopy.284 Photo-stimulated reaction of 1- and 2-haloadamantanes and 1,2- and 1,3-dihaloadamantanes with various carbanionic nucleophiles afforded products rationalized through an SrnI mechanism.285 286 Photolysis of the cycloadduct formed between a functionalized derivative of C6o and diazomethane has been shown to afford a pah of ling-opened structures (125) and (126) via a proposed biradical intermediate (127) (Scheme 19). The UV-photolytic fragments of /-butyl iodide (T and /-Bu ) have been ionized by resonance-enhanced multiphoton ionization for TOF mass spectro-metric analysis.287 A two-dimensional position-sensitive detector provided angular distribution and translational energy data. 

An optical technique involving Doppler spectroscopy can also serve to gain insight into the angular and velocity distributions of reaction products, as reviewed in Ref. [43]. Finally, the Doppler method has been associated with the imaging technique. This is the so-called Doppler-selected time-of-flight technique, which is the most powerful one to obtain information on the three-dimensional (3D) velocity and angular distribution of the reaction products [44-46]. 

As in the case of ketene, the correlated product-state measurements of NCCN at 193.3 nm by FM spectroscopy were also performed in a cell [67], Once again, differences in Doppler profiles between Q and R branches were used to determine vector correlations only v-j correlations were considered to contribute to changes between Q and R branches. As can be seen in Figure 5, now there are distinct differences in the Doppler profile between Q and R branches for NCCN photolysis. The angular distribution of the photoproducts is isotropic [76,79], therefore the Doppler profile in the laboratory frame is given by... 

Conventional molecular beam reactive scattering studies have excelled in the determination of the angular and velocity distributions of reaction products, but direct information on the internal state distributions has been sparse. One of the most important of the non-beam methods for learning about the partitioning of reaction energy into the internal degrees of freedom of the products has been infra-red chemiluminescence studies. Unfortunately, this technique has hitherto been limited to hydride compounds, principally hydrogen halides. We present an alternative technique based on electronic fluorescence spectroscopy. 

For characterizing a dipolar molecule in its electronic ground state, few methods are more instructive than pulsed-nozzle Fourier-trans-form microwave spectroscopy (32). As illustrated schematically in Fig. 5, a short pulse of microwave radiation directed at the gas pulse excites a rotational transition in the species of interest subsequently the rotationally excited molecules reemit radiation, which is detected. This technique provides a remarkably sensitive probe for transients, the properties of which can be specified with all the precision and detail peculiar to rotational spectroscopy only microseconds after their production. In relation to a weakly bound adduct A --B formed by two molecular reagents A and B, for example, we may draw on the rotational spectrum to determine such salient molecular properties as symmetry, radial and angular geometry, the intermolecular stretching force constant and internal dynamics, the electric charge distribution, and the electric dipole and quadrupole moments of A -B (see Table I). 

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