Direct detection of single molecules by optical absorption

The advent of single molecule optics has had a profound impact in fields ranging from biophysics to material science, photophysics, and quantum optics. However, all existing room-temperature single molecule methods have been based on fluorescence detection of highly efficient emitters. Here we demonstrate that standard, modulation-free measurements known from conventional absorption spectrometers can indeed detect single molecules. We report on quantitative measurements of the absorption cross section of single molecules under ambient condition even in their dark state, for example during photoblinking or strong quenching. Our work extends single-molecule microscopy and spectroscopy to a huge class of materials that absorb light but do not fluoresce efficiently.Comment: 15 pages, 4 figure

Detection, spectroscopy and state preparation of a single praseodymium ion in a crystal

Solid-state emitters with atom-like optical and magnetic transitions are highly desirable for efficient and scalable quantum state engineering and information processing. Quantum dots, color centers and impurities embedded in inorganic hosts have attracted a great deal of attention in this context, but influences from the matrix continue to pose challenges on the degree of attainable coherence in each system. We report on a new solid-state platform based on the optical detection of single praseodymium ions via 4f intrashell transitions, which are well shielded from their surroundings. By combining cryogenic high-resolution laser spectroscopy with fluorescence microscopy, we were able to spectrally select and spatially resolve individual ions. In addition to elaborating on the essential experimental steps for achieving this long-sought goal, we demonstrate state preparation and read out of the three ground-state hyperfine levels, which are known to have lifetimes of the order of hundred seconds

Photon Antibunching and Collective Effects in the Fluorescence of Single Bichromophoric Molecules

The fluorescence of individual pairs of perylenemonoimide chromophores coupled via a short rigid linker is investigated. Photon antibunching is reported, indicating collective effects in the fluorescence, which are further substantiated by the observation of collective triplet off times and triplet lifetime shortening. The experimental findings are analyzed in terms of singlet-singlet and singlet-triplet annihilation based on Förster type energy transfer. The results reported here demonstrate that the statistical properties of the emission light of isolated single quantum systems can serve as a hallmark of intermolecular interactions

Light-coupled cryogenic probes to detect low-micromolar samples and allow for an automated NMR platform

Recent advances in NMR fragment screening use sample illumination to boost NMR sensitivity, reduce measurement time to a few seconds, and reduce sample concentration to a few micromolars. Nevertheless, the absence of a fully automated solution to measure several hundreds of samples with photoinduced hyperpolarization limits the large-scale applicability of the method. We present a setup to couple an optical fiber with a cryogenic probe using the flow-cell accessory port. This setup is compatible with commercially available autosamplers, enabling the fully automated measurement of several hundreds of samples per day.</p

Beyond Infrastructure -- Modelling Scholarly Research and Collaboration

International audienceThis paper explores what is needed to foster an acceptance of digital practices in the humanities beyond the creation of pure infrastructure, specifically in terms of understanding and technically modelling traditional scholarly research within a digital medium while enabling new modes of scholarly work that could only be carried out within a digitally-mediated environment

Optical Microscopy in the Nano-World

Scanning near-field optical microscopy (SNOM) is an optical microscopy whose resolution is not bound to the diffraction limit. It provides chemical information based upon spectral, polarization and/or fluorescence contrast images. Details as small as 20 nm can be recognized. Photophysical and photochemical effects can be studied with SNOM on a similar scale. This article reviews a good deal of the experimental and theoretical work on SNOM in Switzerland

Light induced single molecule frequency shift

Alight induced frequency shift of the 0-0 line was measured in two-photon excitation spectra of single diphenyloctatetraene molecules doped in a crystal matrix. The shifts were proportional to the laser power with a slope of about 600 MHz/W when the laser beam of about 300 mW power was focused to a diameter of 2 mu m. Significantly, the observed line broadenings were an order of magnitude smaller than the shifts. The effect is ascribed mainly to a ''fast'' energy exchange between a local vibration and thermal phonons created by the third harmonic C-H band absorption in the matrix, and partially to an ac Stark shift