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Long-term research objective: Matter wave interferometers, in which de Broglie waves are coherently split and then recombined to produce interference fringes, have opened exciting new possibilities for precision and fundamental measurements with complex particles. The aim of our research program is to extend the ideas and techniques of atom optics and atom interferometry which underlie atom inteeferometers, to use these devices to make qualitatively new and/or more precise measurements in atomic physics, and to perform fundamental experiments in quantum mechanics based on our ability to measure interactions that displace the de Broglie wave phase or change the quantum coherence of the beams (reducing the amplitude of the interference pattern).

The development of two-photon lasers and techniques for controlling chaos in fast dynamical systems is described.

The development of a unified picture of short-pulse high-intensity multiphoton processes, embracing atoms, molecules, and solids, appears possible through the study of clusters. Of particular significance are possible intercluster processes that can influence the mechanism of ionization and lead to the production of inner-shell vacancies. Inner-shell excitation leading to prompt X-ray emission is specifically considered and the treatment leads to the definition of a critical cluster size representing the achievement of maximal X-ray emission from the ensemble. These results suggest the possibility of designing a new class of molecular materials optimized for the efficient production and amplification of x-rays. Recent experiments, specifically designed to evaluate certain essential predictions of the cluster picture, have furnished considerable supporting evidence for the main features of the proposed model. These studies, which involved Kr and Xe, (1) established the crucial role of cluster formation in the generation of soft x-ray emission, (2) verified the scaling of this new phenomenon in to the kilovolt region, (3) provided important insights concerning the dynamical character of the strong-field coupling to the clusters and (4) combined the cluster excitation with a recently discovered mode of channeled propagation. These results strongly indicate that the predicted amplification can be achieved.

Using fabricated transmission gratings as optical elements for the matter waves, we are constructing an atom interferometer which will physically separate atom waves before recombining them. Atom interferometers will be useful in studies of atomic properties, tests of basic quantum physics, for metrology, as a rotation sensor, and perhaps ultimately as devices to make ultra-small structures using atom holograms.

For small momenta and low but finite temperatures, the temperature variation of the structure factor represents the population of the elementary excitations. If the temperature is above, the structure factor will decrease first to a minimum before reaching the first peak. This temperature is estimated to be around 2.78 K.

Prepared in cooperation with the Laboratoire de Physique Atomique et Nucleaire, Paris (France) Inst. du Radium and Universite Pierre et Marie Curie, Paris (France). Sponsored in part by Grant NGR-38-003-036.