A novel three-dimensional (3-D) optical memory device is presented that allows fast random access of the information and extremely high bit densities. This device is based on two-photon writing, reading, and erasing of the information in a photochromic material embedded in a polymer matrix. Absorption and emission data show that two-photon writing and reading of information is feasible. The advantages and properties of such a 3-D optical memory are discussed.

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tomers, etc.), it is In harmony with the breadth of meaning implied by the etymology of the term as much as by its widespread usage in technological fields outside of chemistry, and, last but not least, it renders redundant and thus superfluous the term "configurational isomer", whose contradistinction to "conformational isomer" has saddled stereochemistry with a needless dichotomy.45 (44) Mislow, K. "Introduction to Stereochemistry"; W. A. Benjamin: New York, 1965; p 82. (45) (a) A more detailed examination of these and related fundamental questions is reserved for future discussion, (b) For a different approach to the definition of "stereochemical configuration", see: Drozd, V. N.; Zefirov, N. S.;

The photoredox reaction transients of ferrioxalate in water have been studied by means of time-resolved EXAFS and ultrafast optical transient spectroscopy. The transient spectra and kinetics have been measured from the femtosecond to millisecond range, and the Fe-O bond lengths of the ferrioxalate redox reaction transients have been determined with 2 ps time resolution and 0.04 A accuracy. These data in conjunction with quantum-chemistry DFT and UHF calculations were used to formulate a mechanism for the Fe(III) to Fe(II) redox reaction where dissociation precedes electron transfer. In addition, radical scavenging experiments support the mechanism proposed.