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A theory of the cross sections of three-body gas-phase reactions which proceed without activation energy is presented. It is based on the hypothesis that the decomposition of a collision complex is governed by the phase space available to each product under conservation of angular momentum and energy. Calculations on model ion-molecule systems show that the cross section is enhanced if the reaction is exothermic, the final reduced mass is large, and the final long-range attractive forces are large. The theory gives a consistent explanation for the cross sections of the reactions between He+ and H 2 , and He and H2+ which is in satisfactory agreement with experiment.

A new corotational procedure is developed which enables existing finite element formulations to be used in problems that contain arbitrarily large rotations. Through the use of a nonsingular large rotation vector, the contribution of the rigid body motion of the element to the total displacement field is removed before element computations are performed, with the result that almost any element can be easily upgraded to handle large rotations. This paper contains a derivation of the theory, an outline of the implementation into the STAGS code, and a demonstration of performance for problems involving large rotations and moderate strains.

(To be submitted to Nucl. Instr. Meth. A) described. electrons, muons, neutrinos (from missing energy), charged hadrons, ·rr°'s and V°'s is of the detector is its ability to identify particles; the performance in identification of hadrons, and the accuracy obtained in energy and angle is given. An essential property of charged tracks is specified. Calorimeters are used to measure photons and neutral accuracy of the tracking detectors to measure the impact parameter and momentumThe performance of the ALEPH detector at the LEP e+e' collider is reviewed. The Abstract The ALEPH Collaboration" Performance of the ALEPH detector at LEP