Richard J. Saykally

Bio: Richard J. Saykally is an academic researcher from University of California, Berkeley. The author has contributed to research in topics: Spectroscopy & Absorption spectroscopy. The author has an hindex of 94, co-authored 457 publications receiving 40997 citations. Previous affiliations of Richard J. Saykally include University of California & Lawrence Berkeley National Laboratory.

Single Nanowire Lasers

Abstract: Ultraviolet lasing from single zinc oxide nanowires is demonstrated at room temperature. Near-field optical microscopy images quantify the localization and the divergence of the laser beam. The linewidths, wavelengths, and power dependence of the nanowire emission characterize the nanowire as an active optical cavity. These individual nanolasers could serve as miniaturized light sources for microanalysis, information storage, and optical computing.

The effects of dissolved halide anions on hydrogen bonding in liquid water.

Abstract: It is widely believed that the addition of salts to water engenders structural changes in the hydrogen-bond network well beyond the adjacent shell of solvating molecules. Classification of many ions as "structure makers" and "structure breakers" has been based in part on corresponding changes in the vibrational spectra (Raman and IR). Here we show that changes in O-H vibrational spectra induced by the alkali halides in liquid water result instead from the actions of ions' electric fields on adjacent water molecules. Computer simulations that accurately reproduce our experimental measurements suggest that the statistics of hydrogen-bond strengths are only weakly modified beyond this first solvation shell.

Cavity Ringdown Laser Absorption Spectroscopy: History, Development, and Application to Pulsed Molecular Beams.

Abstract: The measurement of electronic spectra of supersonically cooled molecules and clusters is a widely used approach for addressing many problems in chemistry. The most established techniques for making such measurements are laser-induced fluorescence (LIF) and resonance-enhanced multiphoton ionization (REMPI), and both have been employed very successfully in a large number of studies. However, both methods often fail for systems containing more than a few atoms, due to rapid internal conversion, predissociation, or other dynamical processes. Even for small systems, the vibronic band intensities are often contaminated by intramolecular relaxation dynamics; in such cases, these techniques cannot be used for reliable intensity measurements. For clusters that exhibit rapid photofragmentation, depletion spectroscopy can be employed quite effectively to measure their vibronic structure, but again, dynamic effects complicate the interpretation of spectra. The same considerations apply to other types of “action” spectroscopy. It would often be preferable to measure the electronic spectra of molecules and clusters in direct absorption, as this approach is the most straightforward and accurate means of determining absolute vibronic band intensities and for accessing states that are invisible to LIF or REMPI. The problem, of course, is that direct absorption methods are generally orders of magnitude less sensitive than the “action” techniques and are, therefore, difficult to apply to transient species, such as clusters or radicals. In this review, we describe a relatively new direct absorption technique that we have developed for measuring the electronic spectra of jet-cooled molecules and clusters with both high sensitivity and high spectral resolution. The method is based on measurement of the time rate of decay of a pulse of light trapped in a high reflectance optical cavity; we call it cavity ringdown laser absorption spectroscopy (CRLAS). In practice, pulsed laser light is injected into an optical cavity that is formed by a pair of highly reflective (R > 99.9%) mirrors. The small amount of light that is now trapped inside the cavity reflects back and forth between the two mirrors, with a small fraction (∼1 R) transmitting through each mirror with each pass. The resultant transmission of the circulating light is monitored at the output mirror as a function of time and allows the decay time of the cavity to be determined. A simple picture of the cavity decay event for the case where the laser pulse is temporally shorter than the cavity round trip transit time is presented in Figure 1. In this case, the intensity envelope of these discrete transmitted pulses exhibits a simple exponential decay. The time required for the cavity to decay to 1/e of the initial output pulse is called the “cavity ringdown” time. Determination of the ringdown time allows the absolute single pass transmission coefficient of the cavity to be determined with high accuracy, given the mirror spacing. The apparatus is converted to a sensitive absorption spectrometer simply by placing an absorbing medium between the two mirrors and recording the frequency dependent ringdown time of the cavity. Ideally, the ringdown time is a function of only the mirror reflectivities, cavity dimensions, and sample absorption. Absolute absorption intensities are obtained by subtracting the base-line transmission of the cavity, which is determined when the laser wavelength is off-resonance with all molecular transitions. † IBM Predoctoral Fellow. Current address: Sandia National Laboratories, M/S 9055, Livermore, CA 94551-0969. ‡ Los Gatos Research. 25 Chem. Rev. 1997, 97, 25−51

On the nature of ions at the liquid water surface

Abstract: A qualitatively new understanding of the nature of ions at the liquid water surface is emerging Traditionally, the characterization of liquid surfaces has been limited to macroscopic experimental techniques such as surface tension and electrostatic potential measurements, wherein the microscopic picture then has to be inferred by applying theoretical models Because the surface tension of electrolyte solutions generally increases with ion concentration, all inorganic ions have been thought to be repelled from the air-water interface, leaving the outermost surface layer essentially devoid of ions This oversimplified picture has recently been challenged: first by chemical kinetics measurements, then by theoretical molecular dynamics simulations using polarizable models, and most recently by new surface sensitive experimental observations Here we present an overview of the nature of the interfacial structure of electrolyte solutions and give a detailed description of the new picture that is emerging

Measurement of Quantum Tunneling Between Chiral Isomers of the Cyclic Water Trimer

Abstract: A detailed experimental study of the water trimer is reported. A vibration-rotation-tunneling band of the perdeuterated cluster has been measured near 89.6 wave numbers by tunable far infrared laser absorption spectroscopy. The data indicate a chiral six-membered ring structure with rapid quantum tunneling occurring between the enantiomers. The observed vibration involves torsional motion of the water subunits about each hydrogen bond axis. It is speculated that larger water clusters would also exhibit transient chirality and that similar effects may be found in liquid water.

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

The Optical Properties of Metal Nanoparticles: The Influence of Size, Shape, and Dielectric Environment

Abstract: The optical properties of metal nanoparticles have long been of interest in physical chemistry, starting with Faraday's investigations of colloidal gold in the middle 1800s. More recently, new lithographic techniques as well as improvements to classical wet chemistry methods have made it possible to synthesize noble metal nanoparticles with a wide range of sizes, shapes, and dielectric environments. In this feature article, we describe recent progress in the theory of nanoparticle optical properties, particularly methods for solving Maxwell's equations for light scattering from particles of arbitrary shape in a complex environment. Included is a description of the qualitative features of dipole and quadrupole plasmon resonances for spherical particles; a discussion of analytical and numerical methods for calculating extinction and scattering cross-sections, local fields, and other optical properties for nonspherical particles; and a survey of applications to problems of recent interest involving triangula...

Dye-Sensitized Solar Cells

Abstract: Dye-sensitized solar cells (DSCs) offer the possibilities to design solar cells with a large flexibility in shape, color, and transparency. DSC research groups have been established around the worl ...

Quantum Dot Bioconjugates for Ultrasensitive Nonisotopic Detection

Abstract: Highly luminescent semiconductor quantum dots (zinc sulfide-capped cadmium selenide) have been covalently coupled to biomolecules for use in ultrasensitive biological detection. In comparison with organic dyes such as rhodamine, this class of luminescent labels is 20 times as bright, 100 times as stable against photobleaching, and one-third as wide in spectral linewidth. These nanometer-sized conjugates are water-soluble and biocompatible. Quantum dots that were labeled with the protein transferrin underwent receptor-mediated endocytosis in cultured HeLa cells, and those dots that were labeled with immunomolecules recognized specific antibodies or antigens.