Observation of force-detected nuclear magnetic resonance in a homogeneous field

We report the experimental realization of BOOMERANG (better observation of magnetization, enhanced resolution, and no gradient), a sensitive and general method of magnetic resonance. The prototype millimeter-scale NMR spectrometer shows signal and noise levels in agreement with the design principles. We present H-1 and F-19 NMR in both solid and liquid samples, including time-domain Fourier transform NMR spectroscopy, multiple-pulse echoes, and heteronuclear J spectroscopy. By measuring a H-1-F-19 J coupling, this last experiment accomplishes chemically specific spectroscopy with force-detected NMR. In BOOMERANG, an assembly of permanent magnets provides a homogeneous field throughout the sample, while a harmonically suspended part of the assembly, a detector, is mechanically driven by spin-dependent forces. By placing the sample in a homogeneous field, signal dephasing by diffusion in a field gradient is made negligible, enabling application to liquids, in contrast to other force-detection methods. The design appears readily scalable to µm-scale samples where it should have sensitivity advantages over inductive detection with microcoils and where it holds great promise for application of magnetic resonance in biology, chemistry, physics, and surface science. We briefly discuss extensions of the BOOMERANG method to the µm and nm scales

Classification of String-like Solutions in Dilaton Gravity

The static string-like solutions of the Abelian Higgs model coupled to dilaton gravity are analyzed and compared to the non-dilatonic case. Except for a special coupling between the Higgs Lagrangian and the dilaton, the solutions are flux tubes that generate a non-asymptotically flat geometry. Any point in parameter space corresponds to two branches of solutions with two different asymptotic behaviors. Unlike the non-dilatonic case, where one branch is always asymptotically conic, in the present case the asymptotic behavior changes continuously along each branch.Comment: 15 pages, 6 figures. To be published in Phys. Rev.

High Q Cavity Induced Fluxon Bunching in Inductively Coupled Josephson Junctions

We consider fluxon dynamics in a stack of inductively coupled long Josephson junctions connected capacitively to a common resonant cavity at one of the boundaries. We study, through theoretical and numerical analysis, the possibility for the cavity to induce a transition from the energetically favored state of spatially separated shuttling fluxons in the different junctions to a high velocity, high energy state of identical fluxon modes.Comment: 8 pages, 5 figure

NuSTAR Observations of G11.2–0.3

We present in this paper the hard X-ray view of the pulsar wind nebula in G11.2−0.3 and its central pulsar powered pulsar J1811−1925 as seen by NuSTAR. We complement the data with Chandra for a more complete picture and confirm the existence of a hard, power-law component in the shell with photon index Γ = 2.1 ± 0.1, which we attribute to synchrotron emission. Our imaging observations of the shell show a slightly smaller radius at higher energies, consistent with Chandra results, and we find shrinkage as a function of increased energy along the jet direction, indicating that the electron outflow in the PWN may be simpler than that seen in other young PWNe. Combining NuSTAR with INTEGRAL, we find that the pulsar spectrum can be fit by a power law with Γ = 1.32 ± 0.07 up to 300 keV without evidence of curvature

Solving the m-mixing problem for the three-dimensional time-dependent Schr\"{o}dinger equation by rotations: application to strong-field ionization of H2+

We present a very efficient technique for solving the three-dimensional time-dependent Schrodinger equation. Our method is applicable to a wide range of problems where a fullly three-dimensional solution is required, i.e., to cases where no symmetries exist that reduce the dimensionally of the problem. Examples include arbitrarily oriented molecules in external fields and atoms interacting with elliptically polarized light. We demonstrate that even in such cases, the three-dimensional problem can be decomposed exactly into two two-dimensional problems at the cost of introducing a trivial rotation transformation. We supplement the theoretical framework with numerical results on strong-field ionization of arbitrarily oriented H2+ molecules.Comment: 5 pages, 4 figure

Manipulating the torsion of molecules by strong laser pulses

A proof-of-principle experiment is reported, where torsional motion of a molecule, consisting of a pair of phenyl rings, is induced by strong laser pulses. A nanosecond laser pulse spatially aligns the carbon-carbon bond axis, connecting the two phenyl rings, allowing a perpendicularly polarized, intense femtosecond pulse to initiate torsional motion accompanied by an overall rotation about the fixed axis. The induced motion is monitored by femtosecond time-resolved Coulomb explosion imaging. Our theoretical analysis accounts for and generalizes the experimental findings.Comment: 4 pages, 4 figures, submitted to PRL; Major revision of the presentation of the material; Correction of ion labels in Fig. 2(a