Photothermal effects in passive fiber Bragg grating resonators

Photothermal effects in passive Fabry-Perot resonators are caused by the conversion of circulating optical energy into heat as a result of absorption. This results in thermal change in the resonator's optical path length, the round-trip phase, and hence the resonance condition. We describe a simplified dynamic numerical model for photothermal effects in passive fiber Bragg grating resonators and present results of their experimental observation.     

Iron pentacarbonyl: are the axial or the equatorial iron-carbon bonds longer in the gaseous molecule?

The structure of iron pentacarbonyl, Fe(CO)(5), was reinvestigated by gas-phase electron diffraction using an experimental rotational constant available from the literature as a constraint on the structural parameters. The study utilized a B3LYP/6-311+G(d) ab initio quadratic force field, scaled to fit observed infrared wavenumbers, from which were calculated corrections for the effects of vibrational averaging on distances and certain other quantities useful for the structural analysis. The results confirm that the equatorial Fe-C bonds are longer than the axial ones, an important difference with the structure in the crystal where the equatorial Fe-C bonds are the shorter. Some distance (r(g)/A) and vibrational amplitude (l(alpha)/A) parameter values with estimated 2sigma uncertainties based on assumption of D(3h) symmetry are [r(Fe-C)] = 1.829(2), r(Fe-C)(eq) - r(Fe-C)(ax) = 0.032(20), [r(C=O)] = 1.146(2), r(C=O)(eq) - r(C=O)(ax) = 0.006(27), r(Fe-C)(ax) = 1.810(16), r(Fe-C)(eq) = 1.842(11), r(C=O)(ax) = 1.142(23), r(C=O)(eq) = 1.149(16), l(Fe-C)(ax) = l(Fe-C)(eq) = 0.047(5), and l(C=O)(ax) = l(C=O)(eq) = 0.036(3).     

Direct sample fraction deposition using electrospray in narrow-bore size-exclusion chromatography/matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for polymer characterization

A direct sample fraction deposition method was developed for off-line size-exclusion chromatography (SEC)/matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry. By using electrospray, the SEC eluent, together with a suitable matrix solution added coaxially, was directly deposited on the MALDI plate. Owing to the formation of very small droplets in electrospray, solvent evaporation is much faster. The fractionation volume in narrow-bore SEC, which can directly be collected in one MALDI spot, can easily be optimized in the range of a few microlitres. In addition, fairly homogeneous sample spots were obtained. The possible influence of composition variation of the SEC effluent on the analytical results using direct fraction deposition was investigated; no substantial effects were observed. The applicability of the method was demonstrated by characterizing a broad poly(methyl methacrylate) sample. Copyright 2000 John Wiley & Sons, Ltd.     

Experimental demonstration of a squeezing-enhanced power-recycled michelson interferometer for gravitational wave detection

Interferometric gravitational wave detectors are expected to be limited by shot noise at some frequencies. We experimentally demonstrate that a power recycled Michelson with squeezed light injected into the dark port can overcome this limit. An improvement in the signal-to-noise ratio of 2.3 dB is measured and locked stably for long periods of time. The configuration, control, and signal readout of our experiment are compatible with current gravitational wave detector designs. We consider the application of our system to long baseline interferometer designs such as LIGO.     

Squeezing flow of elastic liquids

The theoretical analysis is made of the relation between applied force and plate separation for squeezing flows of viscoelastic liquids between closely-spaced parallel disks. The lubrication approximation and the quasi-steady-state assumption are employed in the development. Elastic effects are incorporated through inclusion of normal stresses. Solutions are presented for liquids with power-law viscometric functions, and a numerical procedure is used for fluids having viscometric functions of arbitrary form. For fast and slow squeezing, calculated values of t_{$\text{1}\text{2}$}, the time required to squeeze out half the fluid, are found to agree with the constant force data of Leider [1,2].     

The atom-cavity system as a generator of quadrature squeezed states

This paper describes experiments with a coupled atom-cavity system generating quadrature squeezed states of light. A wide range of parameters was explored and a regime was found where a beam of laser light with significant power (0.17 mW) and good noise suppression (measured 18±3%, inferred 50±10%) was observed. An analysis of the exact phase of the noise suppression shows it to be a minimum uncertainty state with reduced noise in a combined amplitude/phase quadrature. The observations are in good qualitative agreement with a full quantum theory of squeezing in optical bistability.     

T=1, spin-dipole strength in40Ca

Spin-dipole strength in⁴⁰Ca has been studied by inelastic scattering of 500-MeV protons and the dipole response in⁴⁰Ca is compared with the spin-dipole data from the⁴⁰Ca(p, n) reaction and nonspin-dipole data from photonuclear studies.