| Soft Ionization of Thermally Evaporated Hypergolic Ionic Liquid Aerosols |
04 MAR 2011 |
25 pages |
| Authors:
Christine J. Koh; Chen-Lin Liu; Chris Harmon; Daniel Strasser; Amir Golan; Oleg Kostko; Steven D. Chambreau; Ghanshyam L. Vaghjiani; Stephen R. Leone; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
 | Isolated ion pairs of a conventional ionic liquid, 1-Ethyl-3-Methyl-Imidazolium Bis(trifluoromethylsulfonyl)imide ([Emim+][Tf2N-]), and a reactive hypergolic ionic liquid, 1-Butyl-3-Methyl-Imidazolium Dicyanamide ([Bmim+][Dca-]), are generated by vaporizing ionic liquid aerosol nanoparticles for the first time; the vaporized species are investigated by dissociative ionization with tunable VUV light, exhibiting clear intact cations, Emim+ and Bmim+, presumably originating from intact ion pairs. Mass spectra of ion pair vapor from an effusive source of the hypergolic ... |
|
| Predicting the Density-scaling Exponent of a Glass-forming Liquid from Prigogine-Defay Ratio Measurements |
Jan 2011 |
7 pages |
| Authors:
Ditte Gundermann; Ulf R Pedersen; Tina Hecksher; Nicholas P Bailey; Bo Jakobsen; Tage Christensen; Niels B Olsen; Thomas B Schroeder; Daniel Fragiadakis; Riccardo Casalini; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| Understanding the origin of the dramatic temperature and density dependence of the relaxation time of glass-forming liquids is a fundamental challenge in glass science. The recently established density-scaling relation quantifies the relative importance of temperature and density for the relaxation time in terms of a material-dependent exponent. We show that this exponent for approximate single-parameter liquids can be calculated from thermoviscoelastic linear-response data at a single state point, for instance ... |
|
| In Vitro Analysis of Acetalated Dextran Microparticles as a Potent Delivery Platform for Vaccine Adjuvants |
Jan 2010 |
12 pages |
| Authors:
Eric M Bachelder; Tristan T Beaudette; Kyle E Broaders; Jean M Frechet; Mark T Albrecht; Alfred J Mateczun; Kristy M Ainslie; John T Pesce; Andrea M Keane-Myers; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| Toll-like receptor (TLR) agonists induce potent innate immune responses and can be used in the development of novel vaccine adjuvants. However, access to TLRs can be challenging as exemplified by TLR 7, which Is located intracellularly in endosomal compartments. To increase recognition and subsequent stimulatory effects of TLR 7, imiquimod was encapsulated in acetalated dextran (Ac-DEX) microparticles. Ac-DEX, a water-insoluble and biocompatible polymer,ls relatively stable at pH 7.4, but degrades ... |
|
| Spectroscopy and Dynamics of Transient and Energetic Species |
Apr-2009 |
14 pages |
| Authors:
Daniel M Neumark; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| Free radicals, weakly bound van der Waals complexes, and metal and semiconductor clusters are characterized by photodetachment of the corresponding negative ions using slow electron velocity-map imaging (SEVI), a recently developed, high-resolution (2-3 cm-1) variant of negative ion photoelectron spectroscopy. The SEVI spectrum of a negative ion yields the electron affinity of the neutral, term values for excited states accessible via one-photon detachment, and accurate vibrational frequencies for the ground ... |
|
| Ultrafast Dynamics of Strong-Field Dissociative Ionization of CH2Br2 Probed by Femtosecond Soft X-Ray Transient Absorption Spectroscopy |
24 Jun 2008 |
43 pages |
| Authors:
Zhi-Heng Loh; Stephen R Leone; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| Femtosecond time-resolved soft x-ray transient absorption spectroscopy based on a high-order harmonic generation source is used to investigate the dissociative ionization of CH2Br2 induced by 800 nm strong-field irradiation. At moderate peak intensities (2.0 x 1014 W/cm2), strong-field ionization is accompanied by ultrafast C-Br bond dissociation, producing both neutral Br (2P3/2) and Br* (2P1/2) atoms together with the CH2Br+ fragment ion. The measured rise times for Br and Br* are ... |
|
| Electro-Optic Materials Based Upon Inorganic Semiconductor Nanorod Liquid Crystals |
DEC 2006 |
8 pages |
| Authors:
A. P. Alivisatos; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| In this project we developed a new type of material system for use in opto-electronic applications. It consists of an array of nanorods. The nanorods are quantum semiconductor structures with high fluorescence quantum yields, and with their bandgap emission energy controlled by the diameter of the rod. These quantum rods are coated with a monolayer of organic surfactant which renders them highly soluble in organic liquids. We demonstrated a method ... |
|
| Virus-Based Scaffolds for Organic/Inorganic Hybrid Materials |
2006 |
6 pages |
| Authors:
Matthew Francis; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| The central goal of these studies has been the integration of organic and inorganic components into well-defined structures using chemically functionalized viral capsids. Key strategies that have been explored include the use of new bioconjugation reactions to modify previously inaccessible sites on the protein surfaces and the preparation of water-soluble gold particles bearing reactive groups for biomolecules attachment. We have also developed a method for the attachment to viral capsids ... |
|
| Infrared Cavity Ringdown Spectroscopy of Hydrocarbon Ions and Clusters in Fast Ion Beams |
08 OCT 2004 |
6 pages |
| Authors:
Richard J. Saykally; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| The objectives of this effort were as follows: (1) extend the technical development of pulsed infrared (IR) cavity ringdown spectroscopy to longer wavelengths and higher spectral resolution; (2) develop its capacity as a general tool for trace gas analysis; and (3) study spectra, structures, hydrogen tunneling dynamics of hydrocarbon ions and complexes of relevance to ion- enhanced combustion processes. High-resolution, pulsed infrared cavity ringdown laser spectroscopy was developed and implemented ... |
|
| Nanocrystal Ceramics |
26 JUN 2004 |
17 pages |
| Authors:
A. P. Alivisatos; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| The objectives of this report are as follows: 1) Ceramic and oxide nanocrystals will be prepared and isolated; 2) Nanocrystals will be characterized structurally; 3) Kinetic studies of reaction and phase transition processes in oxide nanocrystals. |
|
| Manipulating Optically Dark States for Quantum Logic |
29 OCT 2002 |
3 pages |
| Authors:
K. B. Whaley; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| We have investigated the use of optically dark states for quantum information processing. We have developed a systematic theoretical approach relating atomic dark states to decoherence-free subspaces and have shown that single qubit manipulations on such dark states are possible to realize with realistic pulse times. We have found a multi-atom dark state in N-atom/cavity systems that can be used to develop an adiabatic ramping scheme to produce N- photon ... |
|
| First Principles Predictions of Gun Tube Erosion Chemistry and Possible Protective Coatings |
SEP 2002 |
16 pages |
| Authors:
Emily A. Carter; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| Increasing the service lifetime of military machinery will improve logistics in the field (less down-time due to maintenance or replacement) and will free up resources for other pressing needs. To this end, the Army has a vested interest in enhancing the lifetime of gun barrels, which are limited currently by erosion of the steel from which the gun barrels are made. However, it is exceedingly difficult to determine experimentally in ... |
|
| Ceramic Nanocrystals |
28 FEB 2002 |
21 pages |
| Authors:
A. P. Alivisatos; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| We have shown that it is possible to prepare disposable nanocrystals of transition metal oxides in the absence of water or air by thermal decomposition of metal Cupferron complexes in hot surfactants. Preliminary experiments suggest that a similar level of size control as in the synthesis of semiconductor nanocrystals is possible. Since the precursor is available for many metal elements, this approach may present a rather general route to metal ... |
|
| Metabolic Engineering of Reactive Cell Surfaces for Controlled Cell Adhesion |
SEP 2001 |
5 pages |
| Authors:
Carolyn R. Bertozzi; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| The objective is to develop techniques for cell surface modification in order to interface cells with synthetic materials in the context of cell- based biosensors. Our approach uses the cell's metabolic machinery for oligosaccharide biosynthesis to deliver novel chemically reactive functional groups to the cell surface. We developed methods for cell adhesion using ketone- hydrazone condensation reactions and a new reaction we developed called the Staudinger ligation. We identified new ... |
|
| Supramolecular Engineering of New Lithium Ion Conducting Polymer Electrolytes |
2001 |
10 pages |
| Authors:
John Arnold; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| This project involves a novel approach to the synthesis of new classes of materials designed to function as ion conducting systems. In particular, our aim is to synthesize materials for use as polymer electrolytes in solid-state lithium batteries. The current phase of this proposed work is designed to identify promising candidates and to study the mechanism by which ions are transported through these new solids. The ultimate goal is to ... |
|
| Synthesis of a Mesomorphic, Columnar, Porphyrin for Fast Li Ion Conducting Electrolytes |
30 OCT 2000 |
9 pages |
| Authors:
John Arnold; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| Most polymer electrolytes, which are usually oxygen-containing systems, rely on polymer segmental motion for ionic conduction. In general, ionic conduction in these electrolytes at ambient temperatures is poor. We proposed, in cooperation with Dr. Larry Scanlon and coworkers, to build and study a single ion conduction channel for lithium ions that eliminates the need for polymer segmental motion for ionic conduction. The basis of this ... |
|
| A Versatile Route to Functionalized Block Copolymers by Nitroxide Mediated 'Living' Free Radical Polymerization |
1999 |
3 pages |
| Authors:
Didier Benoit; Felix Rivera Jr.; Marcelo Piotti; Ian Rees; James L. Hedrick; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| We have recently shown that replacement of TEMPO as the mediating nitroxide in 'living' free radical polymerizations by alpha-hydrogen derivatives leads to monomer selection and functional group compatability approaching that of ATRP based systems. The ability of these new alkoxyamines, such as 1, to mediate the homopolymerization of a wide variety of monomers should permit a much greater range of well defined random, block, and star copolymers to be prepared ... |
|
| DURIP97 Infrared Cavity Ringdown Laser Absorption Spectroscopy: Metal- Containing Clusters and HEDM Molecules |
20 JUL 1998 |
5 pages |
| Authors:
Richard J. Saykally; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| A high resolution infrared cavity ringdown laser absorption spectrometer has been developed to study proposed HEDM molecules and metal containing clusters. Using a novel tunable pulsed Alexandrite ring laser, we are able to generate tunable visible radiation with ca, 40 MHz bandwidth. This tunable visible light is downconverted to the infrared using stimulated Raman scattering in H2 and D2. With this system, tunable radiation from the ... |
|
| Functionalized Nanoporous Polymer Membranes with Well-Defined Pore Architectures via Lyotropic Liquid-Crystalline Monomers |
30 JUN 97 |
10 pages |
| Authors:
Douglas L. Gin; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| Highly ordered, nanoporous polymer membranes were synthesized using polymerizable lyotropic liquid crystals that self-assemble into the inverted hexagonal mesophase as building blocks. The resulting polymer networks contain nanometer-diameter, extended hydrophilic channels that are hexagonally close- packed. Two lyotropic liquid-crystalline monomer platforms have been synthesized. The interchannel separations in the polymerizable materials can be varied in the 30-40 A range by the choice of counterion on the ionic headgroup of the ... |
|
| Combinatorial Strategies Applied to Catalyst Development |
31 MAY 97 |
6 pages |
| Authors:
Johnathan A. Ellman; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| The performed research demonstrates that important ligand classes can be synthesized on solid supports and can be used directly without purification to prepare asymmetric catalysts. For the catalyst system that was evaluated, the ligands prepared in parallel on support provided comparable enantioselectivities to purified ligands prepared individually over several steps in solution. Enantioselectivities greater than 90% ee were observed. These results hold promise for parallel synthesis and evaluation approaches in ... |
|
| Morphology and Property Control in Polymer Thin Films and Membranes through the Use of Self-Assembling Monomers |
28 JAN 97 |
7 pages |
| Authors:
Douglas L. Gin; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| The formation of highly ordered polymer networks using liquid- crystalline (LC) monomers was studied in the context of developing new polymers for use as piezoelectric, dye laser host, and membrane materials. Photopolymerizable, crosslinkable monomers based on thermotropic and lyotropic LC's were sought for these purposes. A precursor to a suitable chiral smectic C monomer for the formation of noncentrosymmetric polymer networks has been synthesized. Two new crosslinkable dye molecules have ... |
|
| Ordered Piezoelectric Networks via a Liquid-Crystalline Monomer Strategy: Synthesis of the LC Monomer |
12 DEC 96 |
7 pages |
| Authors:
B. C. Baxter; D. L. Gin; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| Piezoelectric materials are used in many technological applications. The physical requirements for piezoelectricity are a high degree of bulk order and a noncentrosymmetric bulk structure. Conventional single crystal piezoceramics possess a high degree of order and long term stability; however, they are brittle and difficult to fabricate. Poled piezoelectric polymers offer ease of fabrication and processing; however, they lack long term thermal and mechanical stability. A new technique is described ... |
|
| Photo-Initiated Ion-Molecular Reactions in Size-Selected Clusters |
30 NOV 96 |
3 pages |
| Authors:
Daniel M. Neumark; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| During the grant period, this work has focused on two research areas: zero electron kinetic energy (ZEKE) spectroscopy experiments on mass-selected cluster anions in which a halide ion (C1 or I) is solvated with a known number of rare gas atoms, and stimulated Raman pumping of negative ions. Negative ion ZEKE spectroscopy is a high resolution laser photodetachment experiment which yields information on the vibrational and electronic spectroscopy of both ... |
|
| Laser Spectroscopy of Oxygen Rings, Nitrogen Rings, and Other Novel High Energy Density Forms of Matter |
11 SEP 96 |
22 pages |
| Authors:
Richard J. Saykally; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| New methods are explored for producing and characterizing proposed new HEDM molecules - covalent nitrogen and oxygen rings. A laser ablation 'supersonic catalytic plasma reactor' was developed, wherein a metal target is vaporized by a pulsed UV laser and reactant gases are added to the buffer gas. A pulsed corona discharge nozzle was developed for the same purpose. Cavity Ringdown and VUV laser ionization mass spectroscopy are Laser Absorption Spectroscopy ... |
|
| Novel Biopolymeric Materials |
28 FEB 96 |
5 pages |
| Authors:
Peter G. Schultz; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| Efficient synthetic methods have been generated for the (i) synthesis of libraries of unnatural oligomers, (ii) methods have been developed for the generation and screening of libraries of electronic, magnetic and optical materials, (iii) miniantibodies have been generated which share some of the properties of antibodies themselves. p1 |
|
| Amphiphilic Linear-branched Copolymers and Their Fluorinated Dendritic Analogs |
1996 |
3 pages |
| Authors:
Dong Yu; Jean M. Frechet; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| Copolymers of PEG and analogs of second generation dendrimer have been synthesized and characterized. Normal polyether dendrimers can be replaced by other branched structures with similar physical properties. Incorporation of fluorinated chains enhance the hydrophobicity of the dendrimer. Attachment of long alkyl chains to dendrimers to achieve the same goal is under investigation and applications of the amphiphilic copolymers are being explored. |
|
| Structure and Hydrogen Bond Dynamics of Water-Dimethyl Sulfoxide Mixtures by Computer Simulations |
OCT 93 |
3 pages |
| Authors:
A. Luzar; D. Chandler; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| We have used two different force field models to study concentrated dimethyl sulfoxide (DMSO)-water solutions by molecular dynamics. The results of these simulations are shown to compare well with recent neutron diffraction experiments using H/D isotope substitution A.K. Soper and A. Luzar, J. Chem. Phys. 97, 1320 (1992). Even for the highly concentrated 1DMSO : 2H2O solution, the water hydrogen-hydrogen radial distribution function, gHH(r), exhibits the characteristic tetrahedral ordering of ... |
|
| Combined Neutron Diffraction and Computer Simulation Study of Liquid Dimethyl Sulphoxide |
OCT 93 |
3 pages |
| Authors:
A. Luzar; A. K. Soper; D. Chandler; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| The structure of liquid dimethylsulphoxide (DMSO) at 25 deg C is explored using a combination of neutron diffraction with isotope substitution and computer simulation techniques. The potentials used in the computer simulation consist of Coulomb and 6-12 Lennard-Jones interactions for each of the carbon, oxygen and sulfur sites on the molecule. To interpret the neutron diffraction data most effectively it is necessary to refine both the molecular internal structure and ... |
|
| Application of the Reactive Flux Formalism to Study Water Hydrogen Bond Dynamics |
OCT 93 |
2 pages |
| Authors:
A. Luzar; D. Chandler; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| We performed a molecular dynamics study of water at room temperature to examine the dynamics of hydrogen bond formation. It was carried out through an application of the reactive flux formalism. Computed long time relaxation functions are not consistent with a first-order process. Statistical (non dynamical) theories of hydrogen bond breaking, such as transition state theory with a single dividing surface, are found to be unsatisfactory. Further, our dynamical results ... |
|
| International Symposium on Molecular Beams (14th) Held in Pacific Grove, California on June 7 -12, 1992 |
09 AUG 93 |
493 pages |
| Authors:
Yuan T. Lee; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| The symposium was held on June 7-12, 1992 in Pacific Grove, California. It brought together scientists who work with isolated molecules to share conceptual and practical advances involved with the study of matter in a rarefied, collimated and isolated state represented by the beam. There were 26 invited talks, 25 submitted oral presentations and 78 poster papers in nine sessions on a broad range of topics. The invited talks gave ... |
|
| Quantum Dynamics of Helium Clusters |
MAR 93 |
44 pages |
| Authors:
K. B. Whaley; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| Our study of helium clusters was motivated by the desire to understand the scaling of the unusual properties of bulk 4He, a quantum liquid, in finite size systems as one goes from the macroscopic regime to the regime of molecular dimensions. This is fully in the spirit of general cluster research, namely to develop our understanding of how the transition from molecular to bulk systems (or vice versa) is reflected ... |
|
| Threshold Photodetachment Spectroscopy |
03 SEP 92 |
5 pages |
| Authors:
Daniel M. Neumark; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| The goal of this project is to learn about the electronic and vibrational spectroscopy of size-selected clusters. This is done using high resolution negative ion photodetachment techniques developed in our laboratory during the last four years. In our experiments, a beam of cluster anions (typically Cn- or Sin-) is generated using a laser vaporization source, mass- selected, and photodetached with a fixed frequency or tunable laser. In the fixed-frequency experiments, ... |
|
| Ultra-Low Density Organic-Inorganic Composite Materials Possessing Thermally Insulating and Acoustic Damping Properties |
07 MAY 92 |
13 pages |
| Authors:
Bruce M. Novak; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| We, as well as others, have been interested in the sol-gel process for the synthesis of hybrid inorganic/organic composite materials. Since our first report on the application of tetraalkoxysilanes possessing polymerizable alkoxides for the production of nonshrinking sol-gel composites, we have extended our efforts towards increasing the glass content in these composite materials. The stoichiometry in the tetraalkoxysilanes limits the maximum glass content in the original non-shrinking composites to 10-18%. ... |
|
| Electronically Excited Molecules: Reaction Kinetics and Emission of Light: Nanosecond Infrared Spectroscopy, Electronic Emission from Chemical Reactions |
24 FEB 92 |
7 pages |
| Authors:
C. B. Moore; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| A time-resolved ir absorption spectrometer capable of detecting chemical transients on the nanosecond timescale was designed, constructed, and successfully implemented. The spectrometer was used to characterize the vibrational relaxation of an open shell radical species, CF3, produced with excess energy from the photolysis of the parent CF3I compound. The effects of vibrational excitation in the CF, radical on the reaction CF3 +Br2 CF3Br+ Br were measured. Broadband data collection techniques ... |
|
| Quantum Dynamics of Helium Clusters |
92 |
5 pages |
| Authors:
K. B. Whaley; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| Our study of helium clusters was motivated by the desire to understand the scaling of the unusual properties of bulk (Helium 4), a quantum liquid, in finite size systems as one goes from the macroscopic regime to the regime of molecular dimensions. This is fully in the spirit of general cluster research, namely to develop our understanding of how the transition from molecular to bulk systems (or vice versa) is ... |
|
| Threshold Photodetachment Spectroscopy of C5 |
01 JUL 91 |
16 pages |
| Authors:
T. N. Kitsopoulos; C. J. Chick; V. Zhao; D. M. Neumark; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| The threshold photodetachment spectrum of C5- has been measured. We have observed transitions to the ground and a low-lying excited state of C5. Resolved vibrational structure has been observed as well as spin-orbit fine structure in the negative ion. |
|
| Vibrationally Resolved Spectra of C2-C11 by Anion Photoelectron Spectroscopy |
01 JUL 91 |
46 pages |
| Authors:
D. W. Arnold; S. E. Bradforth; T. N. Kitsopoulos; D. M. Neumark; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| Anion photoelectron spectroscopy has been employed to obtain vibrationally resolved spectra of the carbon molecules C2 through C11. The spectra of C2(-) through C9(-) are dominated by linear anion to linear neutral photodetachment transitions. Linear to linear transitions contribute to the C11(-) spectrum, as well. From these spectra, vibrational frequencies and electron affinities are determined for the linear isomers of C2-C9 and C11. Term values are also obtained for the ... |
|
| Negative Ion Photodetachment as a Probe of the Transition State Region: The I + HI Reaction |
30 APR 91 |
42 pages |
| Authors:
Daniel M. Neumark; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| The study of the transition state of bimolecular reactions using negative ion photodetachment is described. The I + HI reaction is used as an example of this method. The photoelectron spectrum of IHI(-) shows resolved vibrational features assigned to a progression in the antisymmetric stretch mode of the neutral IHI complex. Threshold photodetachment studies of this system at higher resolution show additional structure that arises from two sources: (1) resonances ... |
|
| Study of the Low-Lying Electronic States of Si2 and Si2 Using Negative Ion Photodetachment Techniques |
01 APR 91 |
|
| Authors:
T. N. Kitsopoulos; C. J. Chick; Y. Zhao; D. M. Neumark; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
 | The spectroscopy of elemental clusters has become the focus of much experimental and theoretical research in recent years. A primary goal of these studies is to determine how chemical bonding in a cluster evolves as the number of atoms is varied. A full understanding of bonding in a cluster requires the characterization not only of its ground electronic state, but also of its low- lying excited electronic states. This is ... |
|
| Photoelectron Spectroscopy of Si2 |
15 JAN 91 |
9 pages |
| Authors:
T. N. Kitsopoulos; D. M. Neumark; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| In this report we discuss the photoelectron spectrum of Si2 - obtained at 355 nm. The spectrum shows a series of transition to the low-lying triplet states of Si2 as well as transitions to the higher lying singlet states. Several possible assignments of the anion and neutral triplet states are presented. |
|
| Photochemical Preparation and Spectroscopic Characterization of H4 and Its Decay Products |
NOV 90 |
47 pages |
| Authors:
C. B. Moore; Y. T. Lee; A. H. Kung; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| Three areas of investigation on H4 and its decay products are described: (a) Studies of the effects of rotational and vibrational excitation on the rate of electronic quenching via the maximum ionicity excited state (MIES) for the system H2 (B) + He, and on the rates for angular momentum reorientation for H2(B) in collision with HE, Ne, Ar and molecular hydrogen are reported; (b) A highly sensitive scheme for state-to-state ... |
|
| Vibrationally Resolved Photoelectron Spectra of Si(3)- and Si(4)- |
01 AUG 90 |
17 pages |
| Authors:
T. N. Kitsopoulos; C. J. Chick; A. Weaver; D. M. Neumark; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| Photoelectron spectra of the Si3- and Si4- cluster anions have been obtained at 355 nm and 266 nm. The spectra show transitions to the ground and low-lying excited electronic states of the neutral clusters. Several of the electronic bands show resolved vibrational structure. The electronic state energies and vibrational frequencies are compared to recent ab initio calculations. The Si4- spectrum is consistent with the prediction of a planar, symmetric rhombus ... |
|
| Threshold Photodetachment Spectroscopy of the I + HI Transition State Region |
01 JAN 90 |
18 pages |
| Authors:
I. M. Waller; T. N. Kitsopoulos; D. M. Neumark; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| We have developed a method for probing the transition state region of a neutral bimolecular reaction via photodetachment of a stable negative ion similar in structure to the neutral transition state. In several cases, we have found that the photoelectron spectrum of the hydrogen-bonded anion AHB(-) exhibits resolved vibrational structure which can be assigned to an unstable (AHB) complex located near the transition state for the hydrogen transfer reaction A ... |
|
| Transition State Spectroscopy of Hydrogen Transfer Reactions |
29 NOV 89 |
18 pages |
| Authors:
Daniel M. Neumark; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| The transition state region for several chemical reactions of the type A + HB yields HA + B has been investigated via photodetachment of the stable negative ion AHB-. The photoelectron spectra of BrHBr- and BrHI- show resolved vibrational structure attributable to the transition state region of the Br + HBr and Br + Hi reactions, respectively. The photoelctron spectra of IDI- and the cluster ion IDI-(N2O) are compared; these ... |
|
| High Resolution Threshold Photodetachment Spectroscopy of Negative Ions |
01 MAY 89 |
24 pages |
| Authors:
T. N. Kitsopoulos; I. M. Waller; J. G. Loeser; D. M. Neumark; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| We have designed and constructed a negative ion threshold photodetachment spectrometer with 3/cm (0.37 meV) resolution. Threshold photodetachment spectra of I- and SH- have been obtained. For SH-, individual rotational transitions between the ion and neutral appear as clearly resolved peaks. Keywords: Negative ion photodetachment; Clusters. (MJM) |
|
| Primary Dissociation Processes of Energetic Compounds |
21 NOV 88 |
29 pages |
| Authors:
Yuan T. Lee; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| During the last contract period, we have successfully constructed a very sophisticated and highly sensitive molecular beam apparatus for the investigation of primary thermal and photon induced dissociation processes of polyatomic molecules under isolate conditions. This machine incorporates many new ideas and has been shown to be the best molecular beam apparatus for this purpose in the world. It has enabled us to carry out a series of investigations which ... |
|
| Transient Behaviors in Chemical Reactions: Nanosecond Infrared Spectroscopy, Chemically Pumped Visible and Near-IR Lasers |
JUN 88 |
5 pages |
| Authors:
George C. Pimentel; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| An excimer laser with pulse duration of 28 ns FWHM and average power at 248 nm of 530 mj per pulse was purchased and used as a photolysis source to accompany an existing nanosecond infrared spectrometer. With this system, transient molecular species with lifetimes as short as ten nanoseconds can be investigated. Gaseous CF31 was photolyzed to produce CF3 radicals whose infrared spectra around 1250 wavenumbers were taken at selected ... |
|
| The Infrared Multiphoton Dissociation of Ethyl and Methyl Acetate |
10 NOV 87 |
47 pages |
| Authors:
Eric J. Hintsa; Alec M. Wodtke; Yuan T. Lee; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| The collisionless decomposition of ethyl and methyl acetate was investigated using IR multiphoton dissociation. Ethyl acetate gave 97 percent concerted decomposition producing ethylene and acetic acid, the latter of which underwent significant secondary decomposition to ketene and water. Simple bond rupture producing ethyl radical and CH3CO2, which completely decomposed to CH3 and CO2, accounted for the remaining reaction products. Methyl acetate underwent concerted reaction to produce methanol and ketene, and ... |
|
| Transition Metal Cluster Chemistry |
21 OCT 87 |
|
| Authors:
Peter B. Armentrout; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| Reactions of transition metal cluster ions are examined using guided ion beam techniques. These techniques allow ionic clusters of variable size and composition to be isolated. Measurement of reaction cross sections and branching ratios characterize the interactions of the clusters with a variety of neutral gases. By examining the variation of these quantities with the kinetic energy of the cluster ions, extensive thermochemical data for both ionic and neutral cluster ... |
|
| Design and Synthesis of Semisynthetic Enzymes |
28 JUL 87 |
|
| Authors:
Peter G. Schultz; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| We propose to develop methodology which will for the first time enable specific amino acid residues in proteins to be site-specifically replaced with synthetic amino acid analogues. Amino acids with novel steric, electronic, or spectroscopic properties will then be used to probe structure-function relationships in proteins which lead to receptor/substrate recognition and/or catalysis. We are pursuing a combined chemical/genetic strategy toward this objective. Our approach requires replacement of the codon ... |
|
| Infrared Multiphoton Dissociation of RDX (Hexahydro-1,3,5-trinitro-1,3, 5-triazine) in a Molecular Beam |
07 JUL 87 |
|
| Authors:
Xinsheng Zhao; Eric J. Hintsa; Yuan T. Lee; CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
|
| Infrared multiphoton dissociation (IRMPD) of hexahydro-1,3,5- trinitro-1,3,5-triazine (RDX) in a molecular beam has been performed in order to investigate the mechanism of RDX thermal decomposition. A beam of molecules was crossed by a pulsed TEA CO2 laser and velocity distributions of the various products were measured by the time-of-flight (TOF) technique as a function of the laboratory angle using a mass spectrometric detector. The dissociation channels, their branching ratios, and ... |
|
Reports by Corporate Author
