Anna Lin

Experimental Study of An A+B→C Reaction-Diffusion System in a Capillary: Crossovers from Reaction to Diffusion-Limited Regimes

Continuing work on elementary A+B→C reactions in capillaries, we study the reaction front dynamics of xylanol orange with Cr 3+ in an effectively one-dimentional system with initially separated reactants. This reaction, in contrast to previously studied systems, is not strictly in the diffusion limited regime. i.e. the probability of reaction between species is not unity. Anamalous behavior not seen in the diffusion-limited case has been observed experimentally for the reaction rate, boundary motion, reaction zone width, and local reaction rate. The observed behavior is consistent with recent theoretical studies.

Analyzing power measurements in high‐P2∥ p‐p elastic scattering

The analyzing power in 28 GeV/c proton/proton elastic scattering was measured at P2∥=5.95 and 6.56 (GeV/c)2 using a polarized proton target and an unpolarized proton beam at the Brookhaven National Laboratory AGS. Results indicate that the analyzing power, A, is rising sharply with P2∥.

Scalings of A + B Reaction Kinetics due to Anisotropic Confinements

We report on the diffusion-limited A + B reaction in highly anisotropic spaces. In addition to the highly non-classical behavior of the density of reactants predicted for isotropic spaces, we observe a dimensional crossover in A + B → 0 reactions due to the geometrical compactness of the tubular 2- and 3-dimensional spaces (baguettelike structures). For slabs, we find the crossover time T c . = Wα, which scales as , where a, b and β are given by the earlier and the late time inverse density scalings of ρ − 1 ˜-, t a and ρ −1 - t b W β , respectively. We also obtain a critical width W, below which the chemical reaction progresses without traversing a 2- or 3-dimensional Ovchinnikov-Zeldovich reaction regime. We find that there exist different hierarchies of dimensionally forced crossovers, depending on the initial conditions and geometric restrictions. Kinetic phase diagrams are employed and exponents are given for the A + B elementary reactions in various euclidean geometries. Monte-Carlo simulations illustrate some of the kinetic hierarchies.

Measurement of Spin Effects in pp Elastic Scattering Using the Polarized Beam at the AGS

Using the recently developed 18.5 GeV/c AGS polarized proton beam and a polarized proton target we measured the analyzing power, A, and the spin-spin correlation parameter, Ann, in medium-P2 ⊥ proton-proton elastic scattering. We found sharp dips in both A and Ann, which occur at different P2 ⊥ values. The unexpected sharp structure in the spin-spin force occurs near P2 ⊥ = 2.3 [GeV/c]2 where the elastic cross-section has no apparent structure.