Ultralong coherence times in the purely electronic zero-phonon line emission of single molecules

We report the observation of ultralong coherence times in the purely electronic zero-phonon line emission of single terrylenediimide molecules at 1.4 K. Vibronic excitation and spectrally resolved detection with a scanning Fabry-Perot spectrum analyzer were used to measure a linewidth of 65 MHz. This is within a factor of 1.6 of the transform limit. It therefore indicates that single molecule emission may be suited for applications in linear optics quantum computation. Additionally it is shown that high resolution spectra taken with the spectrum analyzer allow for the investigation of fast spectral dynamics in the emission of a single molecule.Comment: to appear in Applied Physics Letter

A Parallel Mesh-Adaptive Framework for Hyperbolic Conservation Laws

We report on the development of a computational framework for the parallel, mesh-adaptive solution of systems of hyperbolic conservation laws like the time-dependent Euler equations in compressible gas dynamics or Magneto-Hydrodynamics (MHD) and similar models in plasma physics. Local mesh refinement is realized by the recursive bisection of grid blocks along each spatial dimension, implemented numerical schemes include standard finite-differences as well as shock-capturing central schemes, both in connection with Runge-Kutta type integrators. Parallel execution is achieved through a configurable hybrid of POSIX-multi-threading and MPI-distribution with dynamic load balancing. One- two- and three-dimensional test computations for the Euler equations have been carried out and show good parallel scaling behavior. The Racoon framework is currently used to study the formation of singularities in plasmas and fluids.Comment: late submissio

The Life of Forms

In the preliminary work for his Theses On the Concept of History, Walter Benjamin quotes a passage from Henri Focillon’s La vie des formes, using Focillon’s description of classical style for his own notion of the dialectical image. The Essay locates Benjamin’s surprising reception of Focillon in their common interest in a life of forms, not so much in the sense of aesthetic liveliness as defined by Kant (‘Beförderung der Lebendigkeit‘), but in its productiveness of other forms. Focillon’s idea of art history is based on the dynamis or potentiality of artistic shapes giving way to ever new figures and forms. This is not only a key to Benjamin’s concepts of Fortleben/Nachleben in the early Essay The Task of the Translator but also to the ‘dialectical image‘ outlined in the Arcades Project. Benjamin, this Essay argues, refers to Focillon’s life of forms to conceptualise disharmonious and sudden changes of form

Indistinguishable Photons from a Single Molecule

We report the results of coincidence counting experiments at the output of a Michelson interferometer using the zero-phonon-line emission of a single molecule at $1.4 K$. Under continuous wave excitation, we observe the absence of coincidence counts as an indication of two-photon interference. This corresponds to the observation of Hong-Ou-Mandel correlations and proves the suitability of the zero-phonon-line emission of single molecules for applications in linear optics quantum computation.Comment: To appear in Phys. Rev. Let

Quantification Of Flow Aids In Shredded Cheese Blends Using Enzymatic Starch Analysis And Fourier Transform Near-Infrared Spectroscopy

University of Minnesota M.S. thesis.August 2017. Major: Food Science. Advisor: Tonya Schoenfuss. 1 computer file (PDF); vii, 81 pages.Flow aids are commonly used in the production of shredded cheese. It serves as an anticaking agent as well as a carrier for antimycotics and oxygen scavengers to increase shelf-life and quality. There is no current standard method of analysis to confirm the amount of flow aid in shredded cheese. The objective of this research was to develop two methods of analysis for quantification. A total starch assay method was developed to quantify the starch of the flow aid in order to quantify total amount present. With known starch composition of the flow aid, the method was able to accurately analyze total flow aid content to within 0.26% of its true value. A method and calibration using fourier transform near-infrared spectroscopy (NIR) was developed that can accurately analyze total flow aid content of shredded Cheddar cheese to within 0.36% of its true value

Flexible and stable optical parametric oscillator based laser system for coherent anti-Stokes Raman scattering microscopy

The characteristics of a stable and flexible laser system based on a synchronously pumped optical parametric oscillator (OPO) is presented. This OPO can offer very stable operation with both approximately 1 ps and approximately 300 fs outputs over a broad wavelength range, i.e., 920-1200 nm. Combining the pump tuning with the OPO tuning, a total Raman range of 1900-5500 cm(-1) is accessible. For maximum spectral sensitivity, the CARS microsope based on the ps laser system is presented in detail. The lateral resolution of the microscope is diffraction limited to be about 390 nm. Fast wavelength switching (sub-second) between two Raman vibrational frequencies, i.e., 2848 cm(-1) for C--H aliphatic vibrations and 3035 cm(-1) for C--H aromatic vibrations is presented as an example, although this also extends to other Raman frequencies. The possibility of obtaining a multimodal imaging system based on the fs laser system is also discussed

Observation of liquid glass in suspensions of ellipsoidal colloids

Despite the omnipresence of colloidal suspensions, little is known about the influence of shape on phase transformations, especially in nonequilibrium. To date, real-space imaging results are limited to systems composed of spherical colloids. In most natural and technical systems, however, particles are non-spherical and their structural dynamics are determined by translational and rotational degrees of freedom. Using confocal microscopy, we reveal that suspensions of ellipsoidal colloids form an unexpected state of matter, a liquid glass in which rotations are frozen while translations remain fluid. Image analysis unveils hitherto unknown nematic precursors as characteristic structural elements of this state. The mutual obstruction of these ramified clusters prevents liquid crystalline order. Our results give unique insight into the interplay between local structures and phase transformations. This helps to guide applications such as self-assembly of colloidal superstructures and also gives first evidence of the importance of shape on the glass transition in general.Comment: 19 pages, 6 figures; additional SI; submitte

Interference spectroscopy with coherent anti-Stokes Raman scattering of noisy broadband pulses

We propose a new technique for comparing two Raman active samples. The method employs optical interference of the signals generated via coherent anti-Stokes Raman scattering (CARS) of broadband laser pulses with noisy spectra. It does not require spectrally resolved detection, and no prior knowledge about either the Raman spectrum of the samples, or the spectrum of the incident light is needed. We study the proposed method theoretically, and demonstrate it in a proof-of-principle experiment on Toluene and ortho-Xylene samples.Comment: 15 pages, 6 figure