Reagents Molecular Radiators

The high temperatures obtained (220 °C) are not only because of increased boiling points at elevated pressure but also because of a significant contribution from sustained overheating. The yields from the oU-bath experiments were lower than those for the corresponding microwave-heated reactions. In pure, microwave-transparent (non polar) solvents, the added substances, whether ionic or non-ionic, must therefore contribute to the overall temperature profile when the reaction is performed. It seems reasonable that when the substrates act as 

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The study of ion-molecule reactions using state-selected reagents has become a very exciting area of molecular dynamics. We have developed an experimental apparatus in Orsay which utilizes the properties of our tunable synchrotron radiation source at LURE to prepare ions in selected vibronic levels and then to study their reactions. The ions are state-selected using the TPEPICO (threshold-photoelectron/photoion coincidence) method [1]. 

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). 

In the interaction of a coherent laser beam with an ensemble of particles (atoms or molecules), one may treat the individual particles as nearly stationary, because even for a fast atomic/molecular beam the particles move only a few micrometres on the time-scale of the photon interaction. Consequently, if the laser photons are absorbed in the interaction, the coherence properties of the laser radiation are transferred to the particle ensemble. It is this coherence transfer that is exploited in experiments such as the orientation of reagents in chemical reactions, or the probing of intramolecular motion in transition states and orientation of products. 

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