The vibrational predissociation spectroscopy of hydrogen cluster ions

The first infrared spectra of protonated hydrogen clusters in the gas phase have been observed. Predissociation spectra were taken with a tandem mass spectrometer: mass selected hydrogen cluster ions were irradiated inside a rf ion trap by a tunable infrared laser, and the fragment ions created by photodissociation of the clusters were mass selected and detected. Spectra for each product channel were measured by counting fragment ions as a function of laser frequency. Low resolution spectra (Deltanu=10 cm^−1) in the region from 3800 to 4200 cm^−1 were observed for the ions H + 5, H + 7, and H + 9 at 3910, 3980, and 4020 cm−1, respectively. A band was also observed for H + 5 at 3532 cm^−1. No rotational structure was resolved. The frequencies of the band maxima agree well with the frequencies predicted by previous ab initio calculations for the highest modes

General circulation in the atmosphere of Venus driven by polar and diurnal variations of surface temperature

Mathematical model for Venus atmosphere circulation pattern determined by polar and diurnal temperature variation

Infrared spectra of the cluster ions H7O⁺₃·H2 and H9O⁺₄·H2

Infrared spectra of hydrated hydronium ions weakly bound to an H2 molecule, specifically H7O + 3 ·H2 and H9O + 4 ·H2, have been observed. Mass-selected parent ions, trapped in a radio frequency ion trap, are excited by a tunable infrared laser; following absorption, the complex predissociates with loss of the H2, and the resulting fragment ions are detected. Spectra have been taken from 3000 to 4000 cm^−1, with a resolution of 1.2 cm^−1. They are compared to recent theoretical and experimental spectra of the hydronium ion hydrates alone. Binding an H2 molecule to these clusters should only weakly perturb their vibrations; if so, our spectra should be similar to spectra of the hydrated hydronium ions H7O + 3 and H9O + 4

Observation of vortices and hidden pseudogap from scanning tunneling spectroscopic studies of electron-doped cuprate superconductor Sr0.9La0.1CuO2Sr_{0.9}La_{0.1}CuO_2

We present the first demonstration of vortices in an electron-type cuprate superconductor, the highest $T_c$ (= 43 K) electron-type cuprate $Sr_{0.9}La_{0.1}CuO_2$. Our spatially resolved quasiparticle tunneling spectra reveal a hidden low-energy pseudogap inside the vortex core and unconventional spectral evolution with temperature and magnetic field. These results cannot be easily explained by the scenario of pure superconductivity in the ground state of high-$T_c$ superconductivity.Comment: 6 pages, 4 figures. Two new graphs have been added into Figure 2. Accepted for publication in Europhysics Letters. Corresponding author: Nai-Chang Yeh (E-mail: [email protected]

A parallel VLSI architecture for a digital filter of arbitrary length using Fermat number transforms

A parallel architecture for computation of the linear convolution of two sequences of arbitrary lengths using the Fermat number transform (FNT) is described. In particular a pipeline structure is designed to compute a 128-point FNT. In this FNT, only additions and bit rotations are required. A standard barrel shifter circuit is modified so that it performs the required bit rotation operation. The overlap-save method is generalized for the FNT to compute a linear convolution of arbitrary length. A parallel architecture is developed to realize this type of overlap-save method using one FNT and several inverse FNTs of 128 points. The generalized overlap save method alleviates the usual dynamic range limitation in FNTs of long transform lengths. Its architecture is regular, simple, and expandable, and therefore naturally suitable for VLSI implementation

Heterostructure solar cells

The performance of gallium arsenide solar cells grown on Ge substrates is discussed. In some cases the substrate was thinned to reduce overall cell weight with good ruggedness. The conversion efficiency of 2 by 2 cm cells under AMO reached 17.1 percent with a cell thickness of 6 mils. The work described forms the basis for future cascade cell structures, where similar interconnecting problems between the top cell and the bottom cell must be solved. Applications of the GaAs/Ge solar cell in space and the expected payoffs are discussed

Discrete solitons and nonlinear surface modes in semi-infinite waveguide arrays

We discuss the formation of self-trapped localized states near the edge of a semi-infinite array of nonlinear waveguides. We study a crossover from nonlinear surface states to discrete solitons by analyzing the families of odd and even modes centered at different distances from the surface, and reveal the physical mechanism of the nonlinearity-induced stabilization of surface modes.Comment: 4 double-column pages, 5 figures, submitted to Optics Letter