LSST Science Book, Version 2.0

A survey that can cover the sky in optical bands over wide fields to faint magnitudes with a fast cadence will enable many of the exciting science opportunities of the next decade. The Large Synoptic Survey Telescope (LSST) will have an effective aperture of 6.7 meters and an imaging camera with field of view of 9.6 deg^2, and will be devoted to a ten-year imaging survey over 20,000 deg^2 south of +15 deg. Each pointing will be imaged 2000 times with fifteen second exposures in six broad bands from 0.35 to 1.1 microns, to a total point-source depth of r~27.5. The LSST Science Book describes the basic parameters of the LSST hardware, software, and observing plans. The book discusses educational and outreach opportunities, then goes on to describe a broad range of science that LSST will revolutionize: mapping the inner and outer Solar System, stellar populations in the Milky Way and nearby galaxies, the structure of the Milky Way disk and halo and other objects in the Local Volume, transient and variable objects both at low and high redshift, and the properties of normal and active galaxies at low and high redshift. It then turns to far-field cosmological topics, exploring properties of supernovae to z~1, strong and weak lensing, the large-scale distribution of galaxies and baryon oscillations, and how these different probes may be combined to constrain cosmological models and the physics of dark energy.Comment: 596 pages. Also available at full resolution at http://www.lsst.org/lsst/sciboo

C–H Activation and Olefin Insertion as Sources of Multiple Sites in Olefin Polymerization Catalyzed by Cp^AlkylHf(IV) Complexes

Intramolecular activation of hydrocarbyls to form metallacyclic complexes is a relatively fast process in cationic hafnocene catalysts bearing propyl-substituted Cp ligands. The resulting metallacycles are effective 1-hexene polymerization catalysts with activities comparable to that of the nonmetalated precursor. <i>Ad hoc</i> polymerizations of 1-hexene, using (Cp^<i>Pr</i>)₂HfMe₂ as catalyst precursor, allow the isolation and characterization, via nuclear magnetic resonance (NMR) and matrix-assisted laser desorption ionization (MALDI) techniques, of polymers containing (Cp^{<i>CH</i>₂–<i>CH</i>₂–<i>CR</i>₃})₂HfCl₂ (R = H or polymeryl) units. The polymeryl substitutions arise from irreversible incorporation of polymer chains onto the cyclopentadienyl ligand substituent(s) via metallacycle intermediates. As a consequence of such “self-modification”, multiple active sites are generated by a nominally single-site catalyst; this may explain the broadening of the molecular weight distribution (MWD) and chemical composition distribution (CCD) observed in olefin polymerization

Mass Spectrometric Mechanistic Investigation of Ligand Modification in Hafnocene-Catalyzed Olefin Polymerization

We recently reported evidence that a cyclometalated intermediate can facilitate the polymerization of 1-hexene to append polymer chains to the termini of propyl groups of the Me₂Hf­(Cp^{<i>n</i>‑Propyl})₂ catalyst precursor. Herein we provide further mechanistic details on the activation of Me₂Hf­(Cp^{<i>n</i>‑Propyl})₂ by B­(C₆F₅)₃ and the polymerization of 1-hexene mainly by applying a battery of mass spectrometry-based techniques. First, a combination of MALDI and CID fragmentation is used to characterize the high molecular mass region (up to 6 kDa) of the isolated poly­(1-hexene) material with attached metallocene. The CID fragmentation patterns are explained by relatively low-energy ligand losses and higher energy hydrocarbon chain degradation via C–C bond cleavage and 1,3-hydrogen shift reactions. Further mechanistic insights are gained by investigating 1-hexene polymerization reaction employing a properly ¹³C-labeled catalyst activated by B­(C₆F₅)₃. Mass spectrometry analyses, along with supporting NMR experiments, indicate that polymer chain growth from the propylcyclopentadienyl ligand proceeds via a series of 2,1-insertion ring expansions of the hafnium metallacycle. In contrast, free poly­(1-hexene) chains are generated by conventional 1,2-insertions. In addition, six boron-containing species were identified from negative ion mode ESI-QqTOF: [B­(C₆F₅)₃]^−•, [H–B­(C₆F₅)₃]⁻, [CH₃–B­(C₆F₅)₃]⁻, [HO–B­(C₆F₅)₃]⁻, [C₆H₁₃–B­(C₆F₅)₃]⁻, and [B­(C₆F₅)₄]⁻

Physics and technology of the Next Linear Collider: a report submitted to Snowmass '96

We present the current expectations for the design and physics program of an e+e- linear collider of center of mass energy 500 GeV -- 1 TeV. We review the experiments that would be carried out at this facility and demonstrate its key role in exploring physics beyond the Standard Model over the full range of theoretical possibilities. We then show the feasibility of constructing this machine, by reviewing the current status of linear collider technology and by presenting a precis of our `zeroth-order' design