Control of recollision wave packets for molecular orbital tomography using short laser pulses

The tomographic imaging of arbitrary molecular orbitals via high-order harmonic generation requires that electrons recollide from one direction only. Within a semi-classical model, we show that extremely short phase-stabilized laser pulses offer control over the momentum distribution of the returning electrons. By adjusting the carrier-envelope phase, recollisions can be forced to occur from mainly one side, while retaining a broad energy spectrum. The signatures of the semi-classical distributions are observed in harmonic spectra obtained by numerical solution of the time-dependent Schr\"{o}dinger equation.Comment: 8 pages, 4 figures; v2: Added some extra clarifications; v3: minor grammatical change

Exponentially Localized Wannier Functions in Periodic Zero Flux Magnetic Fields

In this work, we investigate conditions which ensure the existence of an exponentially localized Wannier basis for a given periodic hamiltonian. We extend previous results in [Pan07] to include periodic zero flux magnetic fields which is the setting also investigated in [Kuc09]. The new notion of magnetic symmetry plays a crucial role; to a large class of symmetries for a non-magnetic system, one can associate "magnetic" symmetries of the related magnetic system. Observing that the existence of an exponentially localized Wannier basis is equivalent to the triviality of the so-called Bloch bundle, a rank m hermitian vector bundle over the Brillouin zone, we prove that magnetic time-reversal symmetry is sufficient to ensure the triviality of the Bloch bundle in spatial dimension d=1,2,3. For d=4, an exponentially localized Wannier basis exists provided that the trace per unit volume of a suitable function of the Fermi projection vanishes. For d>4 and d \leq 2m (stable rank regime) only the exponential localization of a subset of Wannier functions is shown; this improves part of the analysis of [Kuc09]. Finally, for d>4 and d>2m (unstable rank regime) we show that the mere analysis of Chern classes does not suffice in order to prove trivility and thus exponential localization.Comment: 48 pages, updated introduction and bibliograph

Using Interactive 3D Software to Create Manipulatable Human Figures for Body Perception Research

The poster presents the use of the DAZ3D program as a measurement tool for body size perception. When studying body schema, researchers often rely on human figure comparisons to examine body size perceptions. Often these figures are two-dimensional drawings or photos of human bodies. However, human bodies are three-dimensional. Previous research has shown the advantage of using three-dimensional changeable figures in assessing body size perception (Crossley, Cornelissen, & Tovee, 2012). We chose the DAZ3D program over other options (e.g., Body Visualizer) because it allows the user to rotate the figure in space (both depth and plane), convert manipulated figure measures to real life metrics (e.g., inches or centimeters), input real life metrics to create figures, and manipulate over 50 parameters of measurement consisting of both length and circumference. The downside to DAZ3D is that it can be confusing to set up and use. We explain how to use DAZ3D software effectively for use in body size perception research. We had participants use the DAZ3D software to represent their own body, allowing them to manipulate 17 body measurements. Our data suggests that participants can easily use the program and accurately represent their body size (their figure was compared to real life body measurements). Additionally, because DAZ3D has the ability to manipulate almost all aspects of the human figure (including parameters such as muscle mass), researchers will be able to make a more fine-grained analysis of distortions in body perception in both men and women