Bulletin of the American Physical Society
2005 36th Meeting of the Division of Atomic, Molecular and Optical Physics
Tuesday–Saturday, May 17–21, 2005; Lincoln, Nebraska
Session F1: Undergraduate Research Session |
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Chair: Donald C. Griffin, Rollins College Room: Burnham Yates Conference Center Ballroom I |
Thursday, May 19, 2005 10:30AM - 10:50AM |
F1.00001: Simulated Effects of Odd-Alkane Impurities in a Hexane Monolayer on Graphite Cary L. Pint, M.W. Roth We present the results of molecular dynamics (MD) simulations of odd alkane impurities present within the hexane (even alkane) monolayer. We simulate a series of temperatures at 3\%, 5\%, 10\%, and 15\% impurities of propane (C$_3$H$_8$), pentane (C$_5$H$_{12}$), heptane (C$_7$H$_{16}$), nonane (C$_9$H$_{20}$), and undecane (C$_{11}$H$_{24}$) to study both the changes in the monolayer structure and the phase transitions when odd alkanes, whose low-temperature solid structure has been experimentally observed to be much different than that of hexane, occupy space within the hexane monolayer in the low-temperature herringbone (HB) phase. We find that the most significant changes in the melting transition are imposed by impurities whose chain lengths are much different than that of hexane, and the impurities whose chain lengths most closely resemble hexane still give a melting temperature that is within 10K of the pure hexane monolayer melting temperature at high impurity composition. However, due to ``lattice misfits,'' we find that the transition into the intermediate phase exhibits drastic changes as compared to the pure hexane monolayer with the exception of pentane impurities, whose optimal impurity chain length allows the monolayer to exhibit a commensurate phase that is similar to the hexane monolayer, even with a high impurity composition. [Preview Abstract] |
Thursday, May 19, 2005 10:50AM - 11:10AM |
F1.00002: Optical characteristics of a turbid medium between two mirrors Rebecca Wenning, Q. Su, R. Grobe Using the one-dimensional Boltzmann equation we examine the optical scattering properties of a turbid medium that is located between two mirrors with controllable reflectivity. We examine how the mirrors can be used to enhance the total transmission of an intensity modulated laser beam through this system. The analytical results show that for certain modulation frequencies the total transmission can be increased if the laser source is placed between the mirrors. This finding could improve diffusive imaging for those highly scattering media that are so thick that the laser light would not penetrate sufficiently deep in the absence of any mirrors. This work has been supported by the NSF and Research Corporation. [Preview Abstract] |
Thursday, May 19, 2005 11:10AM - 11:30AM |
F1.00003: High Temperature Calcium Vapor Cell for Absorption Spectroscopy on the Intercombination Line Christopher Erickson, Dallin Durfee, Scott Bergeson We report on construction of a high temperature vapor cell for spectroscopy on the transition from the ground state to the 4s4p-$^3$P$_1$ state in calcium. The cell has a unique dual- chamber design that minimizes calcium loss and prevents window coating. The cell was designed to operate at a temperature of 750 degrees C to produce a vapor density of about 10$^{21}$ atoms/m$^3$. [Preview Abstract] |
Thursday, May 19, 2005 11:30AM - 11:50AM |
F1.00004: Isotopic effect in bond rearrangement caused by sudden single and multiple ionization of water molecules. Mat Leonard, A.M. Sayler, K.D. Carnes, B.D. Esry, I. Ben-Itzhak The production of H$_{2}^{+}$ fragments upon dissociation of water molecules involves rearrangements of the molecular bonds. Using fast ions to ionize a water molecule, electrons can be removed on a time scale of 10 attoseconds, thus freezing the nuclear motion. Our earlier experimental results of H$_{2}^{+}$ + O production rate showed a strong isotopic dependence, which is about two times more likely than D$_{2}^{+}$ + O. Recently, we measured a similar ratio for double ionization of water by 1 MeV/amu F$^{7+}$ projectiles. In particular, the H$_{2}$O$^{2+}$ dissociation into H$_{2}^{+}$ + O$^{+}$ is about twice as large as D$_{2}$O$^{2+} \quad \to $ D$_{2}^{+}$ + O$^{+}$. Finally, we have experimental evidence for H$_{2}^{+}$ formation in triple and quadruple ionization. These first observations of bond rearrangement of multiply ionized molecules indicate a sudden mechanism, i.e. a Franck-Condon-like transition, instead of bonding during the slow dissociation. [Preview Abstract] |
Thursday, May 19, 2005 11:50AM - 12:10PM |
F1.00005: Recombination of a Strongly Magnetized Two-Component Plasma in a Nested Penning-Ioffe Trap A.P. Povilus, J.H. Choi, J.R. Guest, G. Raithel Evidence of three-body recombination of cold $^{85}$Rb ions and electrons is reported in the environment of a nested Penning- Ioffe Trap. Laser-cooled and magnetically trapped $^{85}$Rb atoms are ionized by a pulsed laser, leading to a strongly magnetized cold plasma consisting of slowly moving Rb ions and an electron gas contained in the Penning-Ioffe trap. Recombination leads to the formation of long-lived high-$m$ drift Rydberg states, analagous to those recently observed in cold \={H}. Electric-field ionization techniques are then used to analyze the distribution and evolution of these Rydberg states. Of particular interest are the density and temperature dependence of the recombination rates. We have also studied the stability of simultaneous ion- and neutral-atom trapping in relation to asymmetries inherent in the Penning-Ioffe trapping scheme. [Preview Abstract] |
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