Session D1: Atomic and Molecular Physics

Application of electric fields to alkene-coated cesium vapor cells

Recently, a new alkene-based antirelaxation coating has been discovered [Balabas et al., Phys. Rev. Lett. 105, 070801 (2010)] which enables spin-polarized alkali atoms to bounce off vapor cell walls more than a million times before the spin polarization relaxes, yielding electron spin relaxation times on the order of a minute. This remarkable new technology may open the possibility of conducting a new search for the parity- and time-reversal violating permanent electric dipole moment (EDM) of the electron using a cesium vapor contained in an alkene-coated cell. Previous antirelaxation coatings have demonstrated dramatic vapor density variations upon application and reversal of the large electric fields required for an EDM experiment [Jackson Kimball et al., Phys. Rev. A 79, 032901 (2009)]. We have found that in the new alkene-coated cells these electric-field-induced vapor density variations can be mitigated for particular choices of cell and alkali metal reservoir temperatures. Future work will involve demonstrating the long spin-relaxation times during application and reversal of electric fields and direct measurement of the electric field using the Stark shift of excited states in Cs.   

Proton Impact CH$_{4}$ Scattering below 1.5 keV: A Simulation Study

In recent years the study of charge transfer collision has become one of the most active research areas both experimentally and theoretically. It provides not only the fundamental information for atomic, molecular spectroscopy and many body collision dynamics but also has wide applications in astrophysics and fusion research [1]. We report a study regarding the mechanism of charge transfer and direct elastic scattering of H$^{+}+$ CH$_{4}$ at E \textless 1.5 keV. The applied simulation technique relies on the time dependent density functional theory (TDDFT) [2]. Preliminary analysis of the elastic and inelastic scattering along with the details of our calculations will be presented. \\[4pt] [1] B. H. Bransden and M. R. C. McDowell in \textit{Charge Exchange and the Theory of Ion-Atom Collisions}, (Oxford Press, N.Y., 1992).\\[0pt] [2] E. Runge and E. K. U. Gross, Phys. Rev. Lett. \textbf{52}, 997 (1984).   

YbF, BOB and the eEDM: probing zero with diatomic molecules

The shape of the electron is a fascinating mystery which could prove to unlock a path to physics beyond the standard model. The key to finding this shape, or charge distribution, is a measurement of the electron Electric Dipole Moment, or $e$EDM. The standard model predicts an $e$EDM of less than $10^{-40}e\cdot$cm, but other models, such as string theory, predict values that are orders of magnitude higher. The current experimental upper limit is $\approx 10^{-28}e\cdot$cm, measured with YbF, a diatomic chosen due to huge internal fields in the Yb nucleus. These large fields are essential to resolving the energy level splittings resulting from the $e$EDM. We have performed both Fourier transform microwave spectroscopy and pump-probe optical microwave double resonance spectroscopy on YbF in pursuit of further constraining the Yb nuclear wavefunction, a necessary parameter for the $e$EDM experiments. We present a robust method for fitting multi-isopologue data sets which allows quantitative determination of effects such as the breakdown of approximating the nucleus as a point charge and the breakdown of treating electronic and nuclear wavefunctions as separable.   

The time-dependent Aharonov-Bohm effect

We discuss two possible covariant generalizations of the Aharonov-Bohm effect - one expression in terms of the space-time line integral of the four-vector potential and the other expression in terms of the space-time ``area" integral of the electric and magnetic fields written in terms of the Faraday 2-form. These expressions allow one to calculate the Aharonov-Bohm effect for time-dependent situations. In particular, we use these expressions to study the case of an infinite solenoid with a time varying flux and find that the phase shift is zero due to a cancellation of the Aharonov-Bohm phase shift with a phase shift coming from the Lorentz force associated with the electric field, E = - dA/dt, outside the solenoid. This result may already have been confirmed experimentally.   

Photon Orbital Angular Momentum Spectroscopy

In addition to the photon spin responsible for the two polarization states, photons possess an orbital angular momentum (OAM) with values that are signed integer multiples of h-bar. We present a table-top spectroscopy experiment to generate, manipulate, and measure OAM states of photons from a laser. We create multiple beams with different OAM content using computer generated fork holograms implemented in 35mm film slides. After overlapping the beams into one combined beam, we use multipoint interferometer apertures to generate interference patterns on an imaging detector. Since the different OAM states are orthogonal these patterns sum. A decomposition of the summed pattern is performed using a simple algorithm which retrieves the intensities of each of the original OAM beams. We show several examples of OAM content retrieval via our method.~ This research seeks to perform OAM spectroscopy of natural light sources such as direct and scattered sunlight.   

Electron-Positron Pair Production in Relativistic Laser-Matter Interactions

Ultraintense lasers have been shown to produce large quantities of positrons in a short burst, forming electron-positron pair plasmas, which are analog systems for large-scale astrophysical events such as gamma ray bursts, active galactic nuclei, and black holes. Understanding the pair production mechanisms, and their dependencies to laser and target parameters, is critical to designing and reconstructing astrophysical phenomenon in the laboratory. We have performed preliminary experiments to explore the dominant pair production mechanisms for a range of experimental conditions using the Omega EP laser at the University of Rochester. The Monte Carlo code Geant4 was used to analyze and support experimental evidence. This talk will present the experimental and simulation results.   

A Travelling Wave Group and Consequences

From the TWG for a free particle, $\psi =A(X^{2}/2\sigma^{2}+X)$ where $X=i(kx-\omega t)$; $\sigma $ is an experimental variable; and $A $is a normalizing constant, the following can be derived: the Uncertainty principle [1]; Planck's law; the de Broglie hypothesis; phase velocity; pseudo mass M' [2]; conservation of M'PT [3]; mass as a local excess of energy over momentum. \\[4pt] [1] Bourdillon, A.J., \textit{J. Mod. Phys. }\textbf{3} 290-296 (2012), DOI 10.4236/jmp.2012.33041. \\[0pt] [2] Bourdillon, A.J.,\textit{ J. Mod. Phys. }\textbf{4} 705-711 (2013), DOI 10.4236/jmp.2013.46097. \\[0pt] [3] Bourdillon, A.J., A travelling wave group III, conservation of M'PT, submitted in 2013 to \textit{Phys. Rev. {\&} Res. Int.}   

The Spacetime-Interval does not Distinguish Between Events' Nature

If an event $E_{1}$ occurs at location $L_{1}(x_{1}, y_{1}, z_{1})$ and time $t_{1}$, and another event $E_{2}$ occurs at the location $L_{2}(x_{2}, y_{2}, z_{2})$ and time $t_{2}$, with $t_{1}$ $\le$ $t_{2}$, in the Minkowski spacetime, the squared distance $d^{2}(E_{1}, E_{2})$ between them is the same and equal to: \[ d^{2}(E_{1} ,E_{2} )=c^{2}(t_{2} -t_{1} )^{2}-[(x_{2} -x_{1} )^{2}+(y_{2} -y_{1} )^{2}+(z_{2} -z_{1} )^{2}] \] no matter what kind of events we have! For example, if one has the event \textit{E1}$=$\textit{\textbraceleft John drinks\textbraceright } and the event \textit{E2}$=$\textit{\textbraceleft George eats\textbraceright }, there is no connection between these two events. Or if one has two connected events: \textit{E1}$=$\textit{\textbraceleft Arthur is born\textbraceright } and \textit{E2}$=$\textit{\textbraceleft Arthur dies\textbraceright }. There should be at least one parameter [let's call it ``$N''$] in the above ($\Delta s^{2})$ spacetime coordinate formula representing the \underline {event's nature}.