The Trapping and Characterization of a Single Hydrogen Molecule in a Continuously Tunable Nanocavity

Using inelastic electron tunneling spectroscopy with the scanning tunneling microscope (STM-IETS) and density functional theory calculations (DFT), we investigated properties of a single H2 molecule trapped in nanocavities with controlled shape and separation between the STM tip and the Au (110) surface. The STM tip not only serves for the purpose of characterization, but also is directly involved in modification of chemical environment of molecule. The bond length of H2 expands in the atop cavity, with a tendency of dissociation when the gap closes, whereas it remains unchanged in the trough cavity. The availability of two substantially different cavities in the same setup allows understanding of H2 adsorption on noble metal surfaces and sets a path for manipulating a single chemical bond by design.Comment: 11 pages, 4 figure

The cocked hat: formal statements and proofs of the theorems

Navigators have been taught for centuries to estimate the location of their craft on a map from three lines of position, for redundancy. The three lines typically form a triangle, called a cocked hat. How is the location of the craft related to the triangle? For more than 80 years navigators have also been taught that, if each line of position is equally likely to pass to the right and to the left of the true location, then the likelihood that the craft is in the triangle is exactly 1/4. This is stated in numerous reputable sources, but was never stated or proved in a mathematically formal and rigorous fashion. In this paper we prove that the likelihood is indeed 1/4 if we assume that the lines of position always intersect pairwise. We also show that the result does not hold under weaker (and more reasonable) assumptions, and we prove a generalisation to lines

Quantum entanglement of bound particles under free center of mass dispersion

On the basis of the full analytical solution of the overall unitary dynamics, the time evolution of entanglement is studied in a simple bipartite model system evolving unitarily from a pure initial state. The system consists of two particles in one spacial dimension bound by harmonic forces and having its free center of mass initially localized in space in a minimum uncertainty wave packet. The existence of such initial states in which the bound particles are not entangled is pointed out. The entanglement of the two particles is shown to be independent of the wavepacket mean momentum, and to increase monotonically in a time scale distinct from that of the spreading of the center of mass wavepacket.Comment: 17 pages, 5 figure

Selecting success: assimilation experiences of 1.5 and 2nd generation Mexicans in Seattle

Relatively recent immigration from non-traditional sending areas such as Latin America and Asia reignited scholarship dedicated to understanding and measuring the adaptation and assimilation of immigrants and their descendents. Segmented assimilation theory emerged from this scholarship and predicts three pathways of assimilation for the children of immigrants: positive, downward and selective. I focused on selective assimilation - an assimilation strategy that intentionally preserves culture of origin and maintains relationships to co-nationals and an immigrant community. I explored successful assimilation strategies employed by 1.5 and second generation Mexicans that live in Seattle, Washington. Surveys and interviews administered to a small sample of this population highlighted, as expected, the basic validity of modes of incorporation, human capital and family as keys to assimilation. In-depth interviews provided an emic perspective of what it means to be Mexican and American and the complexity of living biculturally. Interviews revealed further how culture, family and connections to community influenced an individual\u27s advancement. Without exception, participants utilized a composite assimilation strategy that maximized positive aspects of American and Mexican cultures

Near Field Optical Microscopy Characterization of IC Metrology

Images of a microlithographic sample obtained using a new near field scanning optical microscope (NSOM) that uses force regulation of the sample-tip separation are presented. The NSOM is a research instrument fitted with a metal covered glass tip probe that defines a small aperture at the sharp end. The aperture is estimated to be on the order of 100 nanometers in diameter resulting in a resolution exceeding that of diffraction limited systems. This form of microscopy can be done both in the transmission and the reflection modes. The force regulation mechanism produces a simultaneously obtained scanned force microscope (SFM) image of the topography thus permitting correlative imaging of the sample. The samples are imaged in transmission and reflection near field optical format, with white light and with coherent light. The results are compared with other forms of IC imaging and characterization, namely scanned force microscopy (SFM) and scanning electron microscopy (SEM)

Characterization of Atomic Force Microscopy and Electrical Probing Techniques for IC Metrology

A novel atomic force microscope (AFM) is used to image a microlithographic sample. The AFM operates in the non destructive non-contact mode, uses glass tips as opposed to tungsten or silicon, and has an optical interferometric detection system. Its estimated lateral resolution is under 10 nanometers and much better in the z direction. A sample consisting of chrome features on quartz was produced for measurements using AFM and electric probe techniques. The features are single and grouped lines on the order of 1 .tm incorporated into an electric probe pad layout. Dimensions of these features are determined from the AFM images by relating their sizes in pixels to the excursions of the scanners during the formation of the images. These results are compared with measurements obtained through electric probing techniques

Bacterial diversity in the intestinal tract of the funguscultivating termite Macrotermes michaelseni (Sjöstedt)

Microorganisms in the intestinal tracts of termites play a crucial role in the nutritional physiology of termites. The bacterial diversity in the fungus-cultivating Macrotermes michaelseni was examined usingboth molecular and culture dependent methods. Total DNA was extracted from the gut of the termite and 16S rRNA genes were amplified using bacterial specific primers. Representatives from forty-one (41) RFLP patterns from a total of one hundred and two (102) clones were sequenced. Most of the clones were affiliated with 3 main groups of the domain Bacteria: Cytophaga-Flexibacter-Bacteriodes(73), Proteobacteria (13), and the low G+C content Gram-positive bacteria (9). Two RFLPs related to planctomycetes, but deeper branching than known members of the phylum, were detected. In addition, 1 and 2 RFLPs represented the spirochetes and TM7-OP11 groups, respectively. In studies using culture dependent techniques, most of the isolates obtained belonged to the Gram-positive bacteriawith a high G+C content. However, only one of the clones represented Gram-positive bacteria with High G+C content. These results show a high bacterial diversity in the intestinal microbiota of M. michaelseni, which continues to escape cultivation. As is the case in other termites many of the clones represent previously uncultured bacteria. The fact that most of the clones clustered with clones from Macrotermes gilvus provides further support for the hypothesis that microorganisms in intestinal tracts of termites have co-evolved with their hosts

Time Evolution of tunneling and decoherence: soluble model

Decoherence effects associated to the damping of a tunneling two-level system are shown to dominate the tunneling probability at short times in strong coupling regimes in the context of a soluble model. A general decomposition of tunneling rates in dissipative and unitary parts is implemented. Master equation treatments fail to describe the model system correctly when more than a single relaxation time is involved