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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. [ABSTRACT FROM AUTHOR]

The investigation of photochemistry and photophysics of individual quantum systems is described with the help of a wide-field fluorescence microscopy approach. The fluorescence single molecules are observed in real time.

Photo-CIDNP is one among different promising techniques to improve nuclear magnetic resonance (NMR) sensitivity. Being sensitive to particular amino acids makes it a promising candidate with respect to biological NMR. Our goal is to exploit new sensitizers and compare them to the present working horses flavin mononucleotide, bipyridyl, and the recently applied fluorescein. Among the investigated dyes, we found a new and very efficient one, Atto Thio 12, conveniently used in fluorescence microscopy with 2–3 fold enhanced polarization when compared to the established ones. We also show that diode lasers which are now available from near UV to IR can be efficiently used in photo-CIDNP. Results are obtained with the amino acids tyrosine and tryptophan. [ABSTRACT FROM AUTHOR]

The ability to monitor several parameters simultaneously from distinct individual fluorescent reporter molecules facilitates the disentanglement of complex and interacting systems and opens new perspectives in areas from basic science to biopharmaceutical technology. By combining annular illumination microscopy, time-correlated single-photon counting, and multichannel detection, we were able to determine 14 independent parameters from one individual fluorophore. The whole set of parameters was deduced from the few properties of the fluorescence photons, i.e., arrival time, wavelength, and polarization. With this approach, the intensity, the polarization, and the spectral dynamics can be analyzed on a nanosecond time scale and the mean values can be monitored with submillisecond time resolution. Nanosecond spectral dynamics of single molecules has been observed, to the best of our knowledge, for the first time. From our experience, we can determine all parameters for more than 30% of the illuminated fluorophores in biological samples and for more than 80% in doped polymeric films.

Polymer blends into a molecular dispersion transition induced by solid-state tensile deformation was observed using photoluminiscence microscopy.

A method to identify single molecules rapidly and with high efficiency based on simple probability considerations is proposed. In principle, any property of a detected photon in a single-molecule fluorescence experiment, e.g, emission wavelength, arrival time after pulsed excitation, and polarization, can be analyzed within the framework of the outlined methodology. Monte Carlo simulations show that less than 500 photons are needed to assign an observed single molecule to one out of four species with a confidence level higher than 99.9%. We show that single dye molecules of four different dyes embedded in a polymer film can be identified with time-correlated single-photon counting spectrally resolved in two channels.

A study was conducted relating to research on the development of practical applications of persistent spectral hole burning. The experiment focused on the description of the parameters that are pivotal to this area of research and their relation to the structure of the investigated molecules. The scope of the investigation was confined to dye-doped polymers, specifically a porphyrin analogue called meso-diphenyltribenzonaphthoporphyrin in poly(vinyl butyral). Experimental methods and results are presented.

A new hologram type in spectral hole-burning systems is presented. During exposure, the frequency of narrow-band laser light is swept over a spectral range that corresponds to a few homogeneous linewidths of the spectrally selective recording material. Simultaneously the phase of the hologram is adjusted as a function of frequency - the phase sweep function. Because of the phase-reconstructing properties of holography, this recording technique programs the sample as a spectral amplitude and phase filter. We call this hologram type frequency and phase swept (FPS) holograms. Their properties and applications are summarized, and a straightforward theory is presented that describes all the diffraction phenomena observed to date. Thin FPS holograms show strongly asymmetric diffraction into conjugated diffraction orders, which is an unusual behavior for thin transmission holograms. Investigations demonstrate the advantages of FPS holograms with respect to conventional cw recording techniques in frequency-multiplexed data storage. By choosing appropriate phase sweep functions, various features of holographic data storage can be optimized. Examples for cross-talk reduction, highest diffraction efficiency, and maximal readout stability are demonstrated. The properties of these FPS hologram types are deduced from theoretical considerations and confirmed by experiments.

A study examined the bathochromic shift of the lowest-energy electronic transition for the polymers' chromophore and on the width of the inhomogeneously broadened absorption band. Comparison of the measurements of the absorption spectrum in atactic polypropylene with the modeling results indicate that ab initio calculations, semiempirical methods and classical simulations techniques can give significant insights into the complex microscopic interactions in amorphous materials,

The influence of oxygen on the photophysical properties of individual DiI[sub 18] molecules has been investigated by means of both wide field and confocal scanning optical fluorescence microscopy. Excited close to saturation intensity, single-molecule fluorescence detected in wide field by a charge-coupled device camera showed a dramatic increase at exposure to air compared to the fluorescence when the sample was protected from oxygen by nitrogen flush. The change of the triplet lifetime of individual dye molecules due to oxygen quenching was measured in real time by means of time resolved single photon counting. In the presence of oxygen, the triplet state lifetime decreases from several tens of milliseconds down to fractions of a millisecond, whereas no changes of the intersystem crossing quantum yield and the fluorescence lifetime are observed. The triplet lifetimes in the presence and absence of oxygen, respectively, are anti-correlated indicative of heterogeneity of the polymer surrounding the dye molecules. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Studies the absorption spectroscopy on single molecules in solids. Determination of absorption signals of single terrylene molecules in hexadecane and naphthalene crystals at liquid-helium temperatures; Rf signal for the Stark effect modulation; Signal to noise ratios.

The electric field induced superposition of holograms recorded by spectral hole burning is investigated. Holograms have been burned at adjacent positions in a plane defined by wavelength and electric field. Application of an appropriate electric field to the sample causes the components of adjacent holograms to overlap as the spectral holes split due to Stark shifts of molecular transition frequencies. The diffraction efficiency of such superimposed holograms depends on their relative phase and has been studied theoretically and experimentally. It is shown that for zero phase difference, constructive interference leads to a strong diffraction efficiency whereas for a phase difference of π, the gratings cancel leading to zero diffraction efficiency. Experiments have been performed with the dye cresyl violet in a polyvinylbutyral film at a temperature of 1.7 K and the data are compared with computer simulations. [ABSTRACT FROM AUTHOR]

The first paper in this series presented a detailed analysis of the diffraction efficiency of a single holographic grating obtained by spectral hole burning. This paper covers the influence of phase changes which occur during the burning of a single hologram, and the interaction of spectrally adjacent two laser induced gratings. A theoretical description of the holographic efficiencies which takes into account the influence of the relative phases between the two gratings. Experimental results are presented and discussed in terms of the theory. [ABSTRACT FROM AUTHOR]

Holographic detection is compared with the more common transmission method. The signal shapes of the optical holes determined by both techniques are studied theoretically and experimentally as a function of the burning fluence. From a comparison of the transmission signals and the holographic signals, the homogeneous linewidth can be determined. Experimental data was obtained from free base chlorin (1,2-dihydroporphyrin) in a polyvinylbutyral film at a temperature of 1.7 K. From these measurements a homogeneous linewidth of 350 MHz was determined. Limits of sensitivity of the holographic detection method are discussed. [ABSTRACT FROM AUTHOR]