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In time-resolved, single-photon counting experiments, the standard method of nonlinear least-squares curve fitting incorrectly estimates the fluorescence lifetimes. Even for single-exponential data, errors may be up to [+ or -] 15%, and for more complex fits, may be even higher, although the fitted line appears to describe the data. The origin of this error is not a result of the Poisson distribution, as is often stated, but is entirely due to the weighting of the fit. An alternative weighting method involving a minor change in the fitting method eliminates this problem, enabling accurate fitting even in difficult cases, including the small data sets observed in single molecule experiments and with a precision similar to that of maximum likelihood methods.

Given an asymptotically Anti-de Sitter supergravity solution, one can obtain a microscopic interpretation by identifying the corresponding state in the holographically dual conformal field theory. This is of particular importance for heavy pure states that are candidate black hole microstates. Expectation values of light operators in such heavy CFT states are encoded in the asymptotic expansion of the dual bulk configuration. In the D1-D5 system, large families of heavy pure CFT states have been proposed to be holographically dual to smooth horizonless supergravity solutions. We derive the precision holographic dictionary in a new sector of light operators that are superdescendants of scalar chiral primaries of dimension (1,1). These operators involve the action of the supercharges of the chiral algebra, and they play a central role in the proposed holographic description of recently-constructed supergravity solutions known as "supercharged superstrata". We resolve the mixing of single-trace and multi-trace operators in the CFT to identify the combinations that are dual to single-particle states in the bulk. We identify the corresponding gauge-invariant combinations of supergravity fields. We use this expanded dictionary to probe the proposed holographic description of supercharged superstrata, finding precise agreement between gravity and CFT. [ABSTRACT FROM AUTHOR]

The dynamics of the noble-gas liquids underlies that of all liquids making them an important prototypical model system. Using optical Kerr-effect spectroscopy we show that for argon, krypton, and xenon, both the librational and diffusional contributions to the spectrum are surprisingly complex. The diffusional relaxation appears as a stretched-exponential, such as widely found in studies of structured (e.g., glass-forming) liquids and as predicted by mode-coupling theory. We show that this behavior is remarkably similar to that measured in water and suggest that it is a fundamental or universal property. [ABSTRACT FROM AUTHOR]

When salts are added to water, generally the viscosity increases, suggesting that the ions increase the strength of the water’s hydrogen-bond network. However, infrared pump-probe measurements on electrolyte solutions have found that ions have no influence on the rotational dynamics of water molecules, implying no enhancement or breakdown of the hydrogen-bond network. Here, we report optical Kerr effect and dielectric relaxation spectroscopic measurements, which have enabled us to separate the effects of rotational and transitional motions of the water molecules. These data show that electrolyte solutions behave like a supercooled liquid approaching a glass transition in which rotational and translational molecular motions are decoupled. It is now possible to understand previously conflicting viscosity data, nuclear magnetic resonance relaxation, and ultrafast infrared spectroscopy in a single unified picture. [ABSTRACT FROM AUTHOR]

Structural relaxation in the peptide model N-methylacetamide (NMA) is studied experimentally by ultrafast optical Kerr effect spectroscopy over the normal-liquid temperature range and compared to the relaxation measured in water at room temperature. It is seen that in both hydrogen-bonding liquids, β relaxation is present, and in each case, it is found that this can be described by the Cole–Cole function. For NMA in this temperature range, the α and β relaxations are each found to have an Arrhenius temperature dependence with indistinguishable activation energies. It is known that the variations on the Debye function, including the Cole–Cole function, are unphysical, and we introduce two general modifications: One allows for the initial rise of the function, determined by the librational frequencies, and the second allows the function to be terminated in the α relaxation. [ABSTRACT FROM AUTHOR]

An ultrafast optical Kerr effect (OKE) spectroscopy and dielectric relaxation spectroscopy (DRS) are employed to measure the intermolecular dynamics of the 1,3-dialkylimidazolium-based room-temperature ionic liquids (RTILs) [emim][B[F.sub.4]], [emim][DCA], and [bmim][DCA] at 25 degree [Celsius] from below 1 GHz to 10 THz. An intense low frequency (sub-[alpha]) relaxation observed for the RTILs are in accordance with simulations obtained for mesoscopic structure arising from aggregates or clusters-structure that explains the anomalous and inconveniently high viscosities of these liquids.

Energy migration between tryptophan residues is experimented in self-assembled peptide tapes. Depolarization at low pH is not due to rotational diffusion but mainly due to energy migration between adjacent trytophan residues is noted.