Spin dynamics in the carrier-doped S=1/2 triangular lattice of NaxCoO2.yH2O

We probed the local electronic properties of the mixed-valent Co+4-x triangular lattice in NaxCoO2.yH(2)O by 59Co NMR. We observed two distinct types of Co sites for x > or =1/2, but the valence seems averaged out for x approximately 1/3. Local spin fluctuations exhibit qualitatively the same trend down to approximately 100 K regardless of the carrier concentration x, and hence the nature of the electronic ground state. A canonical Fermi-liquid behavior emerges below approximately 100 K only for x approximately 1/3.     

Determining the hydrographic parameters of the surface of water from the image sequences of a CCD camera

Water surface fluctuations were analyzed using image sequences from a CCD (charge coupled device) camera. Both regular and irregular waves were used for the study. A transfer function is obtained by comparing the gray scales of the image and results of in-situ wave gauge array measurements. The effects of non-uniform illumination within the wave basin are imbedded in the transfer function. Thus, the obtained transfer function is directly applicable to all other areas of interests within the wave basin. Estimated wave heights are all in qualitative agreement with those obtained through direct measurements. It is shown that the averaged relative error between these two wave heights is less than 16%.     

Alternating layer and island growth of Pb on Si by spontaneous quantum phase separation

Real-time in situ x-ray studies of continuous Pb deposition on Si(111)-(7x7) at 180 K reveal an unusual growth behavior. A wetting layer forms first to cover the entire surface. Then islands of a fairly uniform height of about five monolayers form on top of the wetting layer and grow to fill the surface. The growth then switches to a layer-by-layer mode upon further deposition. This behavior of alternating layer and island growth can be attributed to spontaneous quantum phase separation based on a first-principles calculation of the system energy.     

Improved direct measurement of the parity-violation parameter Ab using a mass tag and momentum-weighted track charge

We present an improved direct measurement of the parity-violation parameter A(b) in the Z boson-b-quark coupling using a self-calibrating track-charge technique applied to a sample enriched in Z-->bb events via the topological reconstruction of the B hadron mass. Manipulation of the Stanford Linear Collider electron-beam polarization permits the measurement of A(b) to be made independently of other Z-pole coupling parameters. From the 1996-1998 sample of 400,000 hadronic Z decays, produced with an average beam polarization of 73.4%, we find A(b)=0.906+/-0.022(stat)+/-0.023(syst).     

Furan-containing oligoaryl cyclophanene

[structure: see text] Furan-containing oligoaryl cyclophanene 1 and the corresponding cyclophane 2 were synthesized from propargylic dithioacetal 3. The electrochemical and photophysical properties and the fluxional behavior of these molecules have been examined. The emission of 1 appeared at 499 nm whereas that of 2 appeared at 389 nm.     

Wavenumber Measurements of CO(2) Transitions in 1.5-µm Atmospheric Window Using an External-Cavity Diode Laser

Using an external-cavity diode laser (ECDL) as the light source, we have observed the spectrum of CO(2) in the 1.5-μm atmospheric window including the (30(0)1)(I) <-- (00(0)0) and (31(1)1)(I) <-- (01(1)0)(I) bands. Good signal-to-noise ratio allowed us to lock the frequency of our ECDL to the absorption line centers. Wavenumber measurements of the transitions with accuracy about 6.6 x 10(-4) cm(-1) are made with the help of a precision wavemeter calibrated to the accurate C(2)H(2) frequency references in the 1.5-μm wavelength region. Molecular constants are obtained by making the least-squares fits of the measured transition wavenumbers. The rotational and centrifugal distortion constants are consistent with the previous results using high-resolution Fourier transform spectroscopy. However, the band centers are different with previous results by several thousandth reciprocal centimeters. Copyright 2001 Academic Press.     

High-Resolution Measurements of HBr Transitions in the First Overtone Band Using Tunable Diode Lasers

High-resolution absorption lineshapes of the R(7) and P(2) transitions in the first overtone (v = 0-2) band of H(79)Br have been recorded at room temperature using a pair of distributed feedback diode lasers operating near 1.95 and 2.00 μm, respectively. Spectral line intensities and self-broadening coefficients were determined by fitting the measured spectra (for various pressures P = 10-100 Torr) with Voigt profiles and compared with values in the literature. Measured line intensities for the P(2) and R(7) transitions are approximately 11 and 16% higher than those listed in the HITRAN database, respectively. The measured self-broadening coefficient of the P(2) transition is approximately 14% lower than the value listed in HITRAN. Measurements of the P(2) lineshapes at low pressure (100 mTorr) were modeled with eight-line Gaussian profiles based on ground state (v = 0) hyperfine constants to include the effects of nuclear electric quadrupole interactions. Copyright 2000 Academic Press.     

Frequency stabilization of a frequency-doubled 1556-nm source to the 5S(1/2) ? 5D (5/2) two-photon transitions of rubidium

Improvements in the power level of sources near 1550 nm and in the efficiency of waveguide frequency doublers enabled us to lock a frequency-doubled source directly to the 5S(1/2) ? 5D(5/2) two-photon transitions near 778 nm. We obtained a sufficiently powerful second-harmonic signal, exceeding 2 mW, by doubling an external-cavity diode laser that was amplified by an erbium-doped fiber amplifier in a periodically poled LiNbO(3) channel waveguide. Our experimental scheme can be used for realizing compact, high-performance frequency standards near 1550 nm for fiber-optic communication and sensing applications.     

Novel Optical Phase Demodulator Based on a Sampling Phase-Locked Loop

A novel phase-locked coherent demodulator, based on a sampling phase-locked loop, is presented and investigated theoretically. The demodulator is capable of operating at high frequencies, by using optical sampling to downconvert the high-frequency input radio-frequency signal to the frequency range of the baseband loop. We develop a detailed theoretical model of the (sampling) phase-locked coherent demodulator and perform detailed numerical simulations. The simulation results show that the operation of the sampling demodulator resembles the operation of the baseband demodulator for very short optical pulses (<2 ps). Furthermore, we investigate how the signal-to-noise ratio of the demodulator is affected by timing and amplitude jitter of the pulsed optical source