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2000

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Articles 1 - 30 of 463

Full-Text Articles in Physics

Unitarized Pseudoscalar Meson Scattering Amplitudes In Three Flavor Linear Sigma Models, Joseph Schechter, Deirdre Black, Amir H. Fariborz, Sherif Moussa, Salah Nasri Dec 2000

Unitarized Pseudoscalar Meson Scattering Amplitudes In Three Flavor Linear Sigma Models, Joseph Schechter, Deirdre Black, Amir H. Fariborz, Sherif Moussa, Salah Nasri

Physics

The three flavor linear sigma model is studied as a ``toy model'' for understanding the role of possible light scalar mesons in the \pi \pi, \pi K and \pi \eta scattering channels. The approach involves computing the tree level partial wave amplitude for each channel and unitarizing by a simple K-matrix prescription which does not introduce any new parameters. If the renormalizable version of the model is used there is only one free parameter. While this highly constrained version has the right general structure to explain \pi \pi scatteirng, it is ``not quite'' right. A reasonable fit can be made ...


Phase Diagram Of Three-Dimensional Dynamical Triangulations With A Boundary, Simon Catterall, Simeon Warner, Ray Renken Dec 2000

Phase Diagram Of Three-Dimensional Dynamical Triangulations With A Boundary, Simon Catterall, Simeon Warner, Ray Renken

Physics

We use Monte Carlo simulation to study the phase diagram of three-dimensional dynamical triangulations with a boundary. Three phases are indentified and characterized. One of these phases is a new, boundary dominated phase; a simple argument is presented to explain its existence. First-order transitions are shown to occur along the critical lines separating phases.


Optically Induced Periodic Structures In Smectic-C Liquid Crystals, Antal Jákli, A. Vajda, E. Benkler, Janossy, Peter Palffy-Muhoray Dec 2000

Optically Induced Periodic Structures In Smectic-C Liquid Crystals, Antal Jákli, A. Vajda, E. Benkler, Janossy, Peter Palffy-Muhoray

Antal Jakli

We explore periodic structures of smectic-C (SmC) liquid crystals, induced optically by a polarization grating. The studied cells contain a passive surface of rubbed polyimide and an active photosensitive substrate of ate-dye doped polyimide. In a nematic phase the director field can be periodic independent of the angle between the grating vector and the rubbing direction. In the SmA phase periodic structure can be induced only by layer undulations. The SmC behaves similarly to the nematic phase, but the director can rotate only on a cone, which results in a more complex geometry. The periodic pattern is superimposed with four ...


Higher Twist Contributions To R-Hadron Phenomenology In The Light Gluino Scenario, Thomas D. Gutierrez, R. Vogt, J. F. Gunion Dec 2000

Higher Twist Contributions To R-Hadron Phenomenology In The Light Gluino Scenario, Thomas D. Gutierrez, R. Vogt, J. F. Gunion

Physics

The open light gluino window allows non-trivial higher-twist gluino contributions to the proton wave function. Using a two-component model originally developed for charm hadroproduction, higher-twist intrinsic gluino contributions to final-state R-hadron formation are shown to enhance leading-twist production in the forward xnF region. We calculate R-hadron production at Pnlab=800 GeV in pp, pBe, and pCu interactions with light gluino masses of 1.2, 1.5, 3.5, and 5.0 GeV.


Chemical And Dynamical Speciation Of Mobile Ions In The Glassy Fast Ionic Conductor Ag2s+B2s3+Sis2: A 109ag Nuclear Magnetic Resonance Study, Tomoko Akai, Steve W. Martin, Ferdinando Borsa Dec 2000

Chemical And Dynamical Speciation Of Mobile Ions In The Glassy Fast Ionic Conductor Ag2s+B2s3+Sis2: A 109ag Nuclear Magnetic Resonance Study, Tomoko Akai, Steve W. Martin, Ferdinando Borsa

Materials Science and Engineering Publications

109Ag NMR in the highly conductive glass 0.525Ag2S+0.475(0.5B2S3+0.5SiS2) was investigated from 230 to 433 K. The 109Ag NMR spectra reveal for the first time three well resolved lines corresponding to three kinds of chemically speciated Ag ions in sites with different chemical shifts in a macroscopically homogeneous glass. This chemical speciation of Ag ions is discussed in relation to the microstructure of the glass. As the temperature is increased, the three lines that originate from three different species of ions are narrowed, but these lines exist independently up to 433 K, the highest ...


Electrons In Image States Near Roughened Metal Surfaces, Brian K. Clark, Brian W. Gregory, Jean M. Standard Dec 2000

Electrons In Image States Near Roughened Metal Surfaces, Brian K. Clark, Brian W. Gregory, Jean M. Standard

Faculty Publications – Chemistry

Electrons near roughened Ag and Au surfaces with chemisorbed dielectric overlayers of alkanethiol or alkaneselenol self-assembled monolayers are shown to move within the sulfur or selenium head-group layer on the metal terraces. The electrons exist in image states with respect to Ag or Au step edges. There is no substantial image force between the electrons and the terraces.


A Two-Chain Path Integral Model Of Positronium, L. Larrimore, R. N. Mcfarland, P. A. Sterne, Amy Lisa Graves Dec 2000

A Two-Chain Path Integral Model Of Positronium, L. Larrimore, R. N. Mcfarland, P. A. Sterne, Amy Lisa Graves

Physics & Astronomy Faculty Works

We have used a path integral Monte Carlo technique to simulate positronium (Ps) in a cavity. The primitive propagator is used, with a pair of interacting chains representing the positron and electron. We calculate the energy and radial distribution function for Ps enclosed in a hard, spherical cavity, and the polarizability of the model Ps in the presence of an electrostatic field. We find that the positron distribution near the hard wall differs significantly from that for a single particle in a hard cavity. This leads to systematic deviations from predictions of free-volume models which treat Ps as an effective ...


Master Equation For Hydrogen Recombination On Grain Surfaces, Gianfranco Vidali, Ofer Biham, Itay Furman, Valerio Pirronello Dec 2000

Master Equation For Hydrogen Recombination On Grain Surfaces, Gianfranco Vidali, Ofer Biham, Itay Furman, Valerio Pirronello

Physics

Recent experimental results on the formation of molecular hydrogen on astrophysically relevant surfaces under conditions similar to those encountered in the interstellar medium provided useful quantitative information about these processes. Rate equation analysis of experiments on olivine and amorphous carbon surfaces provided the activation energy barriers for the diffusion and desorption processes relevant to hydrogen recombination on these surfaces. However, the suitability of rate equations for the simulation of hydrogen recombination on interstellar grains, where there might be very few atoms on a grain at any given time, has been questioned. To resolve this problem, we introduce a master equation ...


Cross Section For B-Jet Production In P̅P Collisions At √S = 1.8 Tev, B. Abbott, Gregory R. Snow, D0 Collaboration Dec 2000

Cross Section For B-Jet Production In P̅P Collisions At √S = 1.8 Tev, B. Abbott, Gregory R. Snow, D0 Collaboration

Gregory Snow Publications

Bottom-quark production in p̅p collisions at √s = 1.8 TeV is studied with 5 pb-1 of data collected in 1995 by the D0 detector at the Fermilab Tevatron Collider. The differential production cross section for b jets in the central rapidity region (∣yb∣< 1) as a function of jet transverse energy is extracted from a muon-tagged jet sample. Within experimental and theoretical uncertainties, D0 results are found to be higher than, but compatible with, next-to-leading-order QCD predictions.


Phase-Coherent Multilevel Two-Photon Transitions In Cold Rb Atoms: Ultrahigh-Resolution Spectroscopy Via Frequency-Stabilized Femtosecond Laser, Tai Hyun Yoon, Adela Marian, John L. Hall, Jun Ye Dec 2000

Phase-Coherent Multilevel Two-Photon Transitions In Cold Rb Atoms: Ultrahigh-Resolution Spectroscopy Via Frequency-Stabilized Femtosecond Laser, Tai Hyun Yoon, Adela Marian, John L. Hall, Jun Ye

Physics Faculty Contributions

A two-photon transition in cold Rb atoms will be probed with a phase-coherent wide bandwidth femtosecond laser comb. Frequency domain analysis yields a high-resolution picture where phase coherence among various transition pathways through different intermediate states produces interference effects on the resonantly enhanced transition probability. This result is supported by the time domain Ramsey interference effect. The two-photon transition spectrum is analyzed in terms of the pulse repetition rate and carrier frequency offset, leading to a cold-atom-based frequency stabilization scheme for both degrees of freedom of the femtosecond laser.


Low-Frequency Crossover Of The Fractional Power-Law Conductivity In Srruo3, J. S. Dodge, Christopher P. Weber, J. Corson, J. Orenstein, Z. Schlesinger, J. W. Reiner, M. R. Beasley Dec 2000

Low-Frequency Crossover Of The Fractional Power-Law Conductivity In Srruo3, J. S. Dodge, Christopher P. Weber, J. Corson, J. Orenstein, Z. Schlesinger, J. W. Reiner, M. R. Beasley

Physics

We combine the results of terahertz time-domain spectroscopy with far-infrared transmission and reflectivity to obtain the conductivity of SrRuO 3 over an unprecedented continuous range in frequency, allowing us to characterize the approach to zero frequency as a function of temperature. We show that the conductivity follows a simple phenomenological form, with an analytic structure fundamentally different from that predicted by the standard theory of metals.


Ga-Doped Zno Films Grown On Gan Templates By Plasma-Assisted Molecular-Beam Epitaxy, H. J. Ko, Yanfang Chen, S. K. Hong, H. Wenisch, T. Yao, David C. Look Dec 2000

Ga-Doped Zno Films Grown On Gan Templates By Plasma-Assisted Molecular-Beam Epitaxy, H. J. Ko, Yanfang Chen, S. K. Hong, H. Wenisch, T. Yao, David C. Look

Physics Faculty Publications

We have investigated the structural and optical properties of Ga-doped ZnO films grown on GaN templates by plasma-assisted molecular-beam epitaxy. The carrier concentration in Ga-doped ZnO films can be controlled from 1.33×1018/cm3 to 1.13×1020/cm3. Despite high Ga incorporation, the linewidth of (0002) ω-rocking curves of Ga-doped ZnO films still lies in the range from 5 to 15 arc min. Photoluminescence (PL) spectra of Ga-doped ZnO films show dominant near-bandedge emission with negligibly weak deep-level emission, independent of carrier concentration. The PL spectrum exhibits a new emission line at 3.358 ...


Measurement Of The W Boson Mass Using Large Rapidity Electrons, B. Abbott, Gregory R. Snow, D0 Collaboration Dec 2000

Measurement Of The W Boson Mass Using Large Rapidity Electrons, B. Abbott, Gregory R. Snow, D0 Collaboration

Gregory Snow Publications

We present a measurement of the W boson mass using data collected by the DØ. experiment at the Fermilab Tevatron during 1994–1995. We identify W bosons by their decays to en final states where the electron is detected in a forward calorimeter. We extract the W boson mass MW by fitting the transverse mass and transverse electron and neutrino momentum spectra from a sample of 11 089 Weν decay candidates. We use a sample of 1687 dielectron events, mostly due toZee decays, to constrain our model of the detector response. Using the forward calorimeter ...


8 Miles And A Couple Of Antiparticles To Bridgewater State College, Edward Deveney Dec 2000

8 Miles And A Couple Of Antiparticles To Bridgewater State College, Edward Deveney

Bridgewater Review

No abstract provided.


Searches For Neutral Higgs Bosons In Quark-Antiquark Tau-Antitau Final States Using The Opal Detector At Lep, James Andrew Hocker '91 Dec 2000

Searches For Neutral Higgs Bosons In Quark-Antiquark Tau-Antitau Final States Using The Opal Detector At Lep, James Andrew Hocker '91

Doctoral Dissertations

Searches for neutral Higgs bosons have been performed with the OPAL detector at LEP. Approximately 170 /pb of e+e- collision data at a center-of-mass energy of 189 GeV have been used to search for the SM process e+e- to HZ as well as for the processes e+e- to hZ and e+e- to hA which occur in extended Higgs theories. The searches are sensitive to final states containing quarks and tau leptons, for which an artificial neural network for the identification of tau leptons was designed. The results have been combined with OPAL searches for other final ...


Electronic Excitations In Metals And Semiconductors: Ab Initio Studies Of Realistic Many-Particle Systems, Wei Ku Dec 2000

Electronic Excitations In Metals And Semiconductors: Ab Initio Studies Of Realistic Many-Particle Systems, Wei Ku

Doctoral Dissertations

Electronic excitations in metals and semiconductors, measured through inelastic x-ray scattering, electronic energy-loss spectroscopy, and angle-resolved photoemission, provide valuable information about the intrinsic many-body interactions between electrons in the crystal environment. These dynamical interactions are usually analyzed with intuitive simple models. With the problems studied, which correspond to linear response and quasi-particle excitation, it will be shown that ab initio approaches not only can provide more realistic understanding of microscopic processes and mechanisms, but also result in new theoretical interpretations that resolve a number of remarkable "anomalies." Specifically, these problems include the dispersion of the plasmon lifetime in potassium, the ...


Instrument Performance Enhancement And Modification Through An Extended Instrument Paradigm, Stephen L. Mahan Dec 2000

Instrument Performance Enhancement And Modification Through An Extended Instrument Paradigm, Stephen L. Mahan

Doctoral Dissertations

An extended instrument paradigm is proposed, developed and shown in various applications. The CBM (Chin, Blass, Mahan) method is an extension to the linear systems model of observing systems. In the most obvious and practical application of image enhancement of an instrument characterized by a time-invariant instrumental response function, CBM can be used to enhance images or spectra through a simple convolution application of the CBM filter for a resolution improvement of as much as a factor of two. The CBM method can be used in many applications. We discuss several within this work including imaging through turbulent atmospheres, or ...


On The Persistence Of Small Regions Of Vorticity In The Protoplanetary Nebula, S. S. Davis, D. P. Sheehan, J. N. Cuzzi Dec 2000

On The Persistence Of Small Regions Of Vorticity In The Protoplanetary Nebula, S. S. Davis, D. P. Sheehan, J. N. Cuzzi

Physics and Biophysics: Faculty Scholarship

The fate of small regions of vorticity in a barotropic model of the protoplanetary nebula is investigated over thousands of years using a finite difference model. It is found that the coherence time for a small island of vorticity depends on its size, strength, orientation, and radial location in the nebula. Anticyclonic vorticity retains its coherence for longer times than cyclonic vorticity due to favorable interactions with the Keplerian shear flow. Rossby waves are generated as a result of mean vorticity gradients across the disk. The two-dimensional nebula evolves from discrete vortices into an axisymmetric flow consisting of small-amplitude vortex ...


Optical And Magneto-Optical Properties And Electronic Structures Of Single-Crystalline Ral2 (R=Y, La, Ce, Pr, And Lu), R. J. Lange, S. J. Lee, K. J. Kim, Paul C. Canfield, David W. Lynch Dec 2000

Optical And Magneto-Optical Properties And Electronic Structures Of Single-Crystalline Ral2 (R=Y, La, Ce, Pr, And Lu), R. J. Lange, S. J. Lee, K. J. Kim, Paul C. Canfield, David W. Lynch

Physics and Astronomy Publications

The diagonal optical conductivity spectra of single crystals of RAl2 (R=Y, La, Ce, Pr, and Lu) were measured at room temperature by spectroscopic ellipsometry in the 1.5–5.6−eV range. All the compounds exhibit two strong interband absorption peaks at about 1.8 and 3.6 eV for YAl2 and LuAl2, and at about 2.0 and 3.0 eV for LaAl2, CeAl2, and PrAl2. Such differences in the second peak position appear in the theoretical optical conductivity spectra calculated from their band structures obtained by the tight-binding linear-muffin-tin-orbitals method. Most of the contributions to the two ...


Stabilization Of Bound State Decay In An Intense Monochromatic High-Frequency Field, N. L. Manakov, M. V. Frolov, Bogdan Borca, Anthony F. Starace Dec 2000

Stabilization Of Bound State Decay In An Intense Monochromatic High-Frequency Field, N. L. Manakov, M. V. Frolov, Bogdan Borca, Anthony F. Starace

Anthony F. Starace Publications

The formalism of complex quasienergies is used for exact calculation of the field-dependent decay rate for a weakly bound particle (in the model of a three-dimensional zero-range potential) in a strong monochromatic laser field. It is shown that the adiabatic (quasistationary) stabilization regime in this model occurs at frequencies ω exceeding the binding energy and only in a limited intensity range. A simple estimate is obtained for the critical field of stabilization breakdown. The effect may be observed for the decay of H ions in the field of a neodymium laser of femtosecond duration.


The Effects Of Radiation Damage On The Vortex Dynamics Of High Temperature Superconductors, Andra Petrean Dec 2000

The Effects Of Radiation Damage On The Vortex Dynamics Of High Temperature Superconductors, Andra Petrean

Dissertations

This work focuses on the interaction between magnetic vortices in high temperature superconductors and defects introduced by irradiation with protons and heavy ions. The study concentrates on the high temperature superconductor YBa;Cu30 7J5. This material is used to investigate the role of disorder in phase transitions, a topic of great interest in Solid State Physics. In addition, this study analyzes the interaction between vortices and columnar defects in various doses and defect morphologies, including the thermal stability of columnar defects.

We present experimental evidence of the vortex glass phase in proton irradiated Y B a:Cu:!0 -.15. For ...


Surface Diffusion In Mixed Overlayers With Superlattice Ordering: Percolative Transport Around Obstacles And Along Domain Boundaries, Da-Jiang Liu, James W. Evans Dec 2000

Surface Diffusion In Mixed Overlayers With Superlattice Ordering: Percolative Transport Around Obstacles And Along Domain Boundaries, Da-Jiang Liu, James W. Evans

Mathematics Publications

To elucidate surface diffusion in the presence of a coadsorbate with superlattice ordering, we consider particle hopping on a square lattice with some fraction, u B , of quenched blocking sites arranged with checkerboard or c(232) ordering. Behavior for low u B corresponds to diffusion around isolated obstacles, and can be described by exact density expansions. Behavior for high u B corresponds to percolative diffusion along ~or sometimes away from! domain boundaries. The connectivity of these domain boundaries is closely related to the existence of symmetry breaking @i.e., long-range c(232) order# in the distribution of blocking sites. In ...


Surface Segregation And Restructuring Of Colossal-Magnetoresistant Manganese Perovskites La0.65Sr0.35Mno3, Hani Dulli, Peter A. Dowben, Sy-Hwang Liou, E. Ward Plummer Dec 2000

Surface Segregation And Restructuring Of Colossal-Magnetoresistant Manganese Perovskites La0.65Sr0.35Mno3, Hani Dulli, Peter A. Dowben, Sy-Hwang Liou, E. Ward Plummer

Faculty Publications, Department of Physics and Astronomy

We have investigated the surface chemical composition of crystalline films of La0.65Sr0.35MnO3 by angle-resolved x-ray photoelectron spectroscopy. The surface composition was found to be significantly different from that of the bulk because of an appreciable Sr segregation. Furthermore, our study suggests that this Sr segregation has caused a major restructuring of the surface region characterized by the formation of a Ruddlesden-Popper phase (La,Sr)n+1MnnO3n+1 with n = 1. Segregation and restructuring in the surface region should be common in these doped perovskites and will have a profound ...


Questing For The Grail: Core Collapse Supernova Simulations With Boltzmann Neutrino Transport, Otis Earl Messer Dec 2000

Questing For The Grail: Core Collapse Supernova Simulations With Boltzmann Neutrino Transport, Otis Earl Messer

Doctoral Dissertations

The importance of exact neutrino transport in spherically symmetric core collapse supernova simulations is explored in this dissertation. The primary tool for these studies is the neutrino radiation hydrodynamics code AGILE-BOLTZTRAN (Mezzacappa & Bruenn 1993a,b,c; Mezzacappa & Messer 1998; Liebendörfer 2000). AGILE-BOLTZTRAN couples the solution of the Boltzmann equation for all three flavors of neutrinos and antineutrinos to a one-dimensional, implicit, adaptive grid hydrodynamics code. Emission, absorption, and scattering of neutrinos from nucleons and nuclei, neutrino-electron scattering, and pair production and annihilation are included as neutrino-matter couplings. Details of the code are described, including the equations solved and their finite difference representations. The radiation transport algorithm ...


Electronic Structure Of Quasicrystalline Surfaces: Effects Of Surface Preparation And Bulk Structure, V. Fournée, P. J. Pinhero, J. W. Anderegg, Thomas A. Lograsso, A. R. Ross, Paul C. Canfield, I. R. Fisher, Patricia A. Thiel Dec 2000

Electronic Structure Of Quasicrystalline Surfaces: Effects Of Surface Preparation And Bulk Structure, V. Fournée, P. J. Pinhero, J. W. Anderegg, Thomas A. Lograsso, A. R. Ross, Paul C. Canfield, I. R. Fisher, Patricia A. Thiel

Chemistry Publications

We elucidate the nature of the surface electronic properties of quasicrystalline Al-Pd-Mn. We do this by using photoelectron and Auger electron spectroscopies, and by making a variety of comparisons—across types of bulk samples, and across methods of surface preparation. The main conclusions are these: (i) The narrow Mn 2p3/2core-level line observed in the icosahedral phase is a fingerprint of a suppression in the density of states (a pseudogap) at the Fermi level and is not unique to the quasicrystalline phase. It is also independent of the symmetry of the quasicrystalline surface. The Auger line shape is ...


Dynamics Of Signaling Between Ca(2+) Sparks And Ca(2+)- Activated K(+) Channels Studied With A Novel Image-Based Method For Direct Intracellular Measurement Of Ryanodine Receptor Ca(2+) Current, Ronghua Zhuge, Kevin E. Fogarty, Richard A. Tuft, Lawrence M. Lifshitz, Kemal Sayar, John V. Walsh Dec 2000

Dynamics Of Signaling Between Ca(2+) Sparks And Ca(2+)- Activated K(+) Channels Studied With A Novel Image-Based Method For Direct Intracellular Measurement Of Ryanodine Receptor Ca(2+) Current, Ronghua Zhuge, Kevin E. Fogarty, Richard A. Tuft, Lawrence M. Lifshitz, Kemal Sayar, John V. Walsh

Open Access Articles

Ca(2+) sparks are highly localized cytosolic Ca(2+) transients caused by a release of Ca(2+) from the sarcoplasmic reticulum via ryanodine receptors (RyRs); they are the elementary events underlying global changes in Ca(2+) in skeletal and cardiac muscle. In smooth muscle and some neurons, Ca(2+) sparks activate large conductance Ca(2+)-activated K(+) channels (BK channels) in the spark microdomain, causing spontaneous transient outward currents (STOCs) that regulate membrane potential and, hence, voltage-gated channels. Using the fluorescent Ca(2+) indicator fluo-3 and a high speed widefield digital imaging system, it was possible to capture the total ...


Measurement Of The Decay Amplitudes Of B0JK*0 And BS0J/Ψφ Decays, T. Affolder, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Nov 2000

Measurement Of The Decay Amplitudes Of B0 → J/ΨK*0 And BS0 → J/Ψφ Decays, T. Affolder, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

An angular analysis of B0JK*0and Bs0J/ψφ has been used to determine the decay amplitudes with parity-even longitudinal (A0) and transverse (A) polarization and parity-odd transverse (A) polarization. The measurements are based on 190 B0 and 40Bs0candidates obtained from 89 pb-1 of p̅p collisions at the Fermilab Tevatron. The longitudinal decay amplitude dominates with |A0|2= 0.59 ± 0.06 ± 0.01 for B0 and |A0|2 = 0.61 ± 0.14 ± 0.02 for Bs0 decays. The parity-odd ...


The Dissociative Recombination Of The Helium Molecular Ion The Observed Final Products, Luminita Coman Nov 2000

The Dissociative Recombination Of The Helium Molecular Ion The Observed Final Products, Luminita Coman

FIU Electronic Theses and Dissertations

Dissociative recombination reaction has been studied theoretically and experimentally for about four decades. Because of the complexity of this process there is not yet a definite agreement between theory and experiment. In this work, dissociative recombination (DR) of helium molecular ion in thermal plasma was studied using Time of Flight (TOF) spectroscopy. This method allowed the identification of the final atom states products of DR. We found the following final products of the DR of the molecular ion: He(3S; 1s3s), He(1S; 1s3s), He(3P; 1s3p), He(3D; 1s3d), He(1D; 1s3d), He(1 ...


The Hall A Aerogel Čerenkov Detector, Marius Coman Nov 2000

The Hall A Aerogel Čerenkov Detector, Marius Coman

FIU Electronic Theses and Dissertations

The efficiency of the Aerogel Čerenkov detector for detecting particles having velocities greater than the speed of light in the aerogel media and the yield for rejecting particles having subthreshold velocities - smaller than the speed of light in the interaction media - was studied and is presented. The efficiency/inefficiency determination of the Aerogel Čerenkov detector consists of calculating the probabilities that a particle having a velocity above/below threshold generates a photoelectron in the aerogel block. The efficiency is determined using the normalised pulse height distribution of the photoelectrons. The Aerogel Čerenkov detector will play a key role in particle ...


Precision Phase Control Of An Ultrawide-Bandwidth Femtosecond Laser: A Network Of Ultrastable Frequency Marks Across The Visible Spectrum, Jun Ye, John L. Hall, Scott A. Diddams Nov 2000

Precision Phase Control Of An Ultrawide-Bandwidth Femtosecond Laser: A Network Of Ultrastable Frequency Marks Across The Visible Spectrum, Jun Ye, John L. Hall, Scott A. Diddams

Physics Faculty Contributions

We demonstrate that the stability of the current optical frequency comb generated by a Kerr-lens mode-locked femtosecond laser is limited by the microwave reference used for phase locking the comb spacing. Hence we implement precision frequency/phase control of the entire comb to the fundamental and second-harmonic frequencies of a stable cw laser without any external microwave reference. The stability of a cw iodine-stabilized laser is transferred to millions of comb lines (with an instability of 3×10−13) covering more than one octave of the optical frequency spectrum. In addition, the mode spacing of the comb can be used ...