An ab initio treatment of inelastic H + Ne collisions at low energy

On the basis of published quantum chemical data, we calculate the integral cross section for the inelastic process H(1s) + Ne → H(2s, 2p) + Ne for collision energies between threshold and 1.5 keV. Though the quantum chemical data are not completely unambiguous and not so complete as desired, a reasonable agreement between experiment and theory can be achieved.     

Nonresonant charge transfer: Semiclassical calculation of differential cross sections

Charge transfer and elastic scattering differential cross sections in Li⁺ + Na are described in a two state model by a consequent application of semiclassical methods. The coupling model used is Demkov coupling; coupling parameters and potential curves are taken from calculations of other authors. The theoretical results, which contain no adjustable parameters, are in good agreement with experiment.     

MicroDAC strain measurement for electronics packaging structures

Thermo-mechanical reliability concerns in microelectronics and microsystem technology have led to a significant need in information on stress/strain behavior inside microscopic components under load. Because of the decreasing size of structures new measurement tools have to be developed in order to assure future experimental access. Strain measurement from load state micrographs utilizing correlation techniques seems to be one of the promising approaches. Its application to thermally stressed objects in electronics packaging is the main topic of this paper. Deformation measurements are presented for solder interconnects of flip chip and chip scale packages. Emphasis is made for the experimental support of finite element simulation by means of experimental validation of mechanical modeling. Furthermore, a wide variety of new packaging materials and material compounds are to be characterized. Different material properties for bulk material and microscopic structures intensify the search for new testing methods. Again correlation algorithms can be applied to measure strains on microscopic areas and subsequently to obtain material properties. The feasibility to measure coefficients of thermal expansion and Poisson ratios on tiny specimens is demonstrated in the paper.     

Quantum Zeno and anti-Zeno paradoxes

Continuous observation of a time independent projection operator is known to prevent change of state (the quantum Zeno paradox). We discuss the recent result that generic continuous measurement of time dependent projection operators will in fact ensure change of state: an anti-Zeno paradox.     

NaXe potentials from interference structures in optical collisions

Experimental differential cross sections for the optical collision process Na(3s)²S + Xe + hν → Na(3p)²P + Xe are presented. By comparison with the results of accurate quantum calculations, the observed oscillatory structure is used to investigate the X²Σ and B²Σ potential curves of the NaXe van der Waals molecule. The repulsive branches of both curves are probed in addition to the binding minimum of the ground state. A value of 92 cm^-1 is obtained for the dissociation energy.     

Analysis of hydrogen Lyα emission by the intensity variation in an electric field

Direct and cascade contributions to the Lyα intensity from collisionally excited hydrogen atoms can partly be distinguished by the intensity variation in an external electric field.     

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Quantum and semiclassical dynamics of differential optical collisions

We apply quantum and semiclassical theories to differential optical collisions Na(3²S_1/2) + Kr + Na(3²P_1/2,3/2) + Kr. Our results provide a basis to analyze recent experiments in which for the first time optical collisions were investigated with angular resolution under crossed-beam conditions. A characteristic feature of the differential cross sections is the pronounced oscillatory structure due to interferences of different Condon paths. These Stueckelberg oscillations form an extremely sensitive probe of the collisional dynamics and of the molecular interactions. We demonstrate perspectives to determine geometric properties of the collision complex by excitation with polarized light. By final state analysis nonadiabatic (spin-orbit, rotational) interactions can be studied with complete control of the path. In summary it is shown that the method of differential detection of optical collisions opens a variety of new accesses to atomic and molecular subcollisions. Received: 30 July 1997 / Received in final form: 5 November 1997 / Accepted: 8 January 1998