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Full-Text Articles in Physical Sciences and Mathematics

(E,2e) Study Of Two-Center Interference Effects In The Ionization Of N₂, Leigh R. Hargreaves, Christopher J. Colyer, Mark A. Stevenson, B. Lohmann, Ola A. Al-Hagan, Don H. Madison, Chuangang Ning Dec 2009

(E,2e) Study Of Two-Center Interference Effects In The Ionization Of N₂, Leigh R. Hargreaves, Christopher J. Colyer, Mark A. Stevenson, B. Lohmann, Ola A. Al-Hagan, Don H. Madison, Chuangang Ning

Physics Faculty Research & Creative Works

A number of previous studies have suggested the possibility of two-center interference effects in the single ionization of diatomic molecules such as H2 and N2. While interference effects have been successfully observed in the ionization of H2, to date evidence for interference in N2 ionization has yet to be conclusively demonstrated. This study presents triply differential cross sections for electron impact ionization of N2, measured using the (e,2e) technique. The data are probed for signatures of two-center interference effects. Evidence for interference manifesting in the cross sections is observed.


Nonlinear Evolution Of Baryon Acoustic Oscillations From Improved Perturbation Theory In Real And Redshift Spaces, Atsushi Taruya, Takahiro Nishimichi, Shun Saito, Takashi Hiramatsu Dec 2009

Nonlinear Evolution Of Baryon Acoustic Oscillations From Improved Perturbation Theory In Real And Redshift Spaces, Atsushi Taruya, Takahiro Nishimichi, Shun Saito, Takashi Hiramatsu

Physics Faculty Research & Creative Works

We study the nonlinear evolution of baryon acoustic oscillations in the matter power spectrum and correlation function from the improved perturbation theory (PT). Based on the framework of renormalized PT, which provides a nonperturbative way to treat the gravitational clustering of large-scale structure, we apply the closure approximation that truncates the infinite series of loop contributions at one-loop order, and obtain a closed set of integral equations for power spectrum and nonlinear propagator. The resultant integral expressions are basically equivalent to those previously derived in the form of evolution equations, and they keep important nonperturbative properties which can dramatically improve ...


Systematic Analysis Of Double-Ionization Dynamics Based On Four-Body Dalitz Plots, Daniel Fischer, Michael Schulz, Katharina R. Schneider, Marcelo F. Ciappina, Tom Kirchner, Aditya H. Kelkar, S. Hagman, Manfred Grieser, Kai Uwe Kuhnel, Robert Moshammer, Joachim Hermann Ullrich Dec 2009

Systematic Analysis Of Double-Ionization Dynamics Based On Four-Body Dalitz Plots, Daniel Fischer, Michael Schulz, Katharina R. Schneider, Marcelo F. Ciappina, Tom Kirchner, Aditya H. Kelkar, S. Hagman, Manfred Grieser, Kai Uwe Kuhnel, Robert Moshammer, Joachim Hermann Ullrich

Physics Faculty Research & Creative Works

We report on an experimental and theoretical systematic study of double ionization of helium by ion impact in terms of four-particle Dalitz plots. Several collision systems covering abroad range of perturbation parameters η (projectile charge to speed ratio) were investigated. With increasing η we observe a systematic trend from features, characteristic to correlated double-ionization mechanisms, to signatures of higher-order processes not requiring electron-electron correlations [the mechanism called "two-step-two projectile-electron interaction" (TS-2)]. The data for the largest η can qualitatively be amazingly well described by a simple model only including the TS-2 mechanism.


Four-Body Model For Transfer Excitation, Allison L. Harris, Jerry Peacher, Don H. Madison, James Colgan Dec 2009

Four-Body Model For Transfer Excitation, Allison L. Harris, Jerry Peacher, Don H. Madison, James Colgan

Physics Faculty Research & Creative Works

We present here a four-body model for transfer-excitation collisions, which we call the four-body transfer-excitation (4BTE) model. Each two-body interaction is explicitly included in the 4BTE model, allowing us to study the effects of individual two-body interactions. We apply our model to fully differential cross sections for proton+helium collisions, and study the effect of the incident projectile-atom interaction, the scattered projectile-ion interaction, the projectile-nuclear interaction, and electron correlation within the target atom.


Correlated Two-Photon Emission By Transitions Of Dirac-Volkov States In Intense Laser Fields: Qed Predictions, Erik Lotstedt, Ulrich D. Jentschura Nov 2009

Correlated Two-Photon Emission By Transitions Of Dirac-Volkov States In Intense Laser Fields: Qed Predictions, Erik Lotstedt, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

In an intense laser field, an electron may decay by emitting a pair of photons. The two photons emitted during the process, which can be interpreted as a laser-dressed double Compton scattering, remain entangled in a quantifiable way: namely, the so-called concurrence of the photon polarizations gives a gauge-invariant measure of the correlation of the hard gamma rays. We calculate the differential rate and concurrence for a backscattering setup of the electron and photon beam, employing Volkov states and propagators for the electron lines, thus accounting nonperturbatively for the electron-laser interaction. The nonperturbative results are shown to differ significantly compared ...


Nuclear Form Factor, Validity Of The Equivalent Photon Approximation And Coulomb Corrections To Muon Pair Production In Photon-Nucleus And Nucleus-Nucleus Collisions, Ulrich D. Jentschura, V. G. Serbo Nov 2009

Nuclear Form Factor, Validity Of The Equivalent Photon Approximation And Coulomb Corrections To Muon Pair Production In Photon-Nucleus And Nucleus-Nucleus Collisions, Ulrich D. Jentschura, V. G. Serbo

Physics Faculty Research & Creative Works

We study in detail the influence of the nuclear form factor both on the Born cross section and on the Coulomb corrections to the photo-production of muon pairs off heavy nuclei (γ Z→μ + μ - Z) and in heavy-ion collisions (ZZ→ZZ μ + μ -). Our findings indicate a number of issues which have not been sufficiently described as yet in the literature: (i) the use of a realistic form factor, based on the Fermi charge distribution for the nucleus, is absolutely indispensable for reliable theoretical predictions; (ii) we checked quantitatively that the equivalent photon approximation has a very good accuracy ...


Analysis Of Angular Dependence Of Strong-Field Tunneling Ionization For Co₂, Song-Feng Zhao, Cheng Jin, Anh-Thu Le, T. F. Jiang, C. D. Lin Nov 2009

Analysis Of Angular Dependence Of Strong-Field Tunneling Ionization For Co₂, Song-Feng Zhao, Cheng Jin, Anh-Thu Le, T. F. Jiang, C. D. Lin

Physics Faculty Research & Creative Works

We analyzed the discrepancy of the angular dependence of strong-field ionization for CO₂ among the different theoretical calculations and experiments. Using a more accurate ground-state wave function of CO₂ in the asymptotic region, we showed that the accuracy in the earlier tunneling ionization theory of Tong et al. [Phys. Rev. A 66, 033402 (2002)] is much improved. We also concluded that the angular dependence deduced from the experiment of Pavicic [Phys. Rev. Lett. 98, 243001 (2007)] appears to be too narrowly distributed.


Search For Gravitational-Wave Bursts In The First Year Of The Fifth Ligo Science Run, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Nov 2009

Search For Gravitational-Wave Bursts In The First Year Of The Fifth Ligo Science Run, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

We present the results obtained from an all-sky search for gravitational-wave (GW) bursts in the 64-2000 Hz frequency range in data collected by the LIGO detectors during the first year (November 2005-November 2006) of their fifth science run. The total analyzed live time was 268.6 days. Multiple hierarchical data analysis methods were invoked in this search. The overall sensitivity expressed in terms of the root-sum-square (rss) strain amplitude hrss for gravitational-wave bursts with various morphologies was in the range of 6 x 10-22 Hz -1/2 to a few x 10-21Hz-1/2. No GW ...


Search For High Frequency Gravitational-Wave Bursts In The First Calendar Year Of Ligo's Fifth Science Run, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Nov 2009

Search For High Frequency Gravitational-Wave Bursts In The First Calendar Year Of Ligo's Fifth Science Run, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

We present an all-sky search for gravitational waves in the frequency range 1 to 6 kHz during the first calendar year of LIGO's fifth science run. This is the first untriggered LIGO burst analysis to be conducted above 3 kHz. We discuss the unique properties of interferometric data in this regime. 161.3 days of triple-coincident data were analyzed. No gravitational events above threshold were observed and a frequentist upper limit of 5.4 year-1 on the rate of strong gravitational-wave bursts was placed at a 90% confidence level. Implications for specific theoretical models of gravitational-wave emission are ...


Nonlinear Power Spectrum In The Presence Of Massive Neutrinos: Perturbation Theory Approach, Galaxy Bias, And Parameter Forecasts, Shun Saito, Masahiro Takada, Atsushi Taruya Oct 2009

Nonlinear Power Spectrum In The Presence Of Massive Neutrinos: Perturbation Theory Approach, Galaxy Bias, And Parameter Forecasts, Shun Saito, Masahiro Takada, Atsushi Taruya

Physics Faculty Research & Creative Works

Future or ongoing galaxy redshift surveys can put stringent constraints on neutrinos masses via the high-precision measurements of galaxy power spectrum, when combined with CMB information. In this paper we develop a method to model galaxy power spectrum in the weakly nonlinear regime for a mixed dark matter [cold dark matter (CDM) plus finite-mass neutrinos] model, based on perturbation theory (PT) whose validity is well tested by simulations for a CDM model. In doing this we carefully study various aspects of the nonlinear clustering (nonlinear neutrino perturbations and the higher-order growth functions), and then arrive at a useful approximation allowing ...


Nonperturbative Treatment Of Double Compton Backscattering In Intense Laser Fields, Erik Lotstedt, Ulrich D. Jentschura Sep 2009

Nonperturbative Treatment Of Double Compton Backscattering In Intense Laser Fields, Erik Lotstedt, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

The emission of a pair of entangled photons by an electron in an intense laser field can be described by two-photon transitions of laser-dressed, relativistic Dirac-Volkov states. In the limit of a small laser field intensity, the two-photon transition amplitude approaches the result predicted by double Compton scattering theory. Multiexchange processes with the laser field, including a large number of exchanged laser photons, cannot be described without the fully relativistic Dirac-Volkov propagator. The nonperturbative treatment significantly alters theoretical predictions for future experiments of this kind. We quantify the degree of polarization correlation of the photons in the final state by ...


Search For Gravitational Wave Ringdowns From Perturbed Black Holes In Ligo S4 Data, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Sep 2009

Search For Gravitational Wave Ringdowns From Perturbed Black Holes In Ligo S4 Data, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

According to general relativity a perturbed black hole will settle to a stationary configuration by the emission of gravitational radiation. Such a perturbation will occur, for example, in the coalescence of a black hole binary, following their inspiral and subsequent merger. At late times the waveform is a superposition of quasinormal modes, which we refer to as the ringdown. The dominant mode is expected to be the fundamental mode, l = m = 2. Since this is a well-known waveform, matched filtering can be implemented to search for this signal using LIGO data. We present a search for gravitational waves from black ...


First Ligo Search For Gravitational Wave Bursts From Cosmic (Super)Strings, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Sep 2009

First Ligo Search For Gravitational Wave Bursts From Cosmic (Super)Strings, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

We report on a matched-filter search for gravitational wave bursts from cosmic string cusps using LIGO data from the fourth science run (S4) which took place in February and March 2005. No gravitational waves were detected in 14.9 days of data from times when all three LIGO detectors were operating. We interpret the result in terms of a frequentist upper limit on the rate of gravitational wave bursts and use the limits on the rate to constrain the parameter space (string tension, reconnection probability, and loop sizes) of cosmic string models. Many grand unified theory-scale models (with string tension ...


On The Transition Rate Of The Fe X Red Coronal Line, Gunter Brenner, Jose R. Crespo Lopez-Urrutia, Sven Bernitt, Daniel Fischer, Rainer Ginzel, Kai Uwe Kuhnel, Volkhard Mackel, Paul H. Mokler, Martin C. Simon, Joachim Hermann Ullrich Sep 2009

On The Transition Rate Of The Fe X Red Coronal Line, Gunter Brenner, Jose R. Crespo Lopez-Urrutia, Sven Bernitt, Daniel Fischer, Rainer Ginzel, Kai Uwe Kuhnel, Volkhard Mackel, Paul H. Mokler, Martin C. Simon, Joachim Hermann Ullrich

Physics Faculty Research & Creative Works

We present a lifetime measurement of the 3s 23p 5 2 Po 1/2 first excited fine-structure level of the ground state configuration in chlorine-like Fe X, which relaxes to the ground state through a magnetic dipole (M1) transition (the so-called red coronal line) with a wavelength accurately determined to 637.454(1) nm. Moreover, the Zeeman splitting of line was observed. The lifetime of 14.2(2) ms is the most precise one measured in the red wavelength region and agrees well with advanced theoretical predictions and an empirically scaled interpolation based on experimental values from the ...


Einstein@Home Search For Periodic Gravitational Waves In Early S5 Ligo Data, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Aug 2009

Einstein@Home Search For Periodic Gravitational Waves In Early S5 Ligo Data, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

This paper reports on an all-sky search for periodic gravitational waves from sources such as deformed isolated rapidly spinning neutron stars. The analysis uses 840 hours of data from 66 days of the fifth LIGO science run (S5). The data were searched for quasimonochromatic waves with frequencies f in the range from 50 to 1500 Hz, with a linear frequency drift ḟ (measured at the solar system barycenter) in the range -f/τ < ḟ < 0.1f/τ, for a minimum spin-down age τ of 1000 years for signals below 400 Hz and 8000 years above 400 Hz. The main computational work of ...


Relativistic (Zα)2 Corrections And Leading Quantum Electrodynamic Corrections To The Two-Photon Decay Rate Of Ionic States, Benedikt J. Wundt, Ulrich D. Jentschura Aug 2009

Relativistic (Zα)2 Corrections And Leading Quantum Electrodynamic Corrections To The Two-Photon Decay Rate Of Ionic States, Benedikt J. Wundt, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

We calculate the relativistic corrections of relative order (Zα) 2 to the two-photon decay rate of higher excited S and D states in ionic atomic systems, and we also evaluate the leading radiative corrections of relative order α (Zα) 2 ln [(Zα) -2]. We thus complete the theory of the two-photon decay rates up to relative order α3 ln (α). An approach inspired by nonrelativistic quantum electrodynamics is used. We find that the corrections of relative order (Zα) 2 to the two-photon decay are given by the Zitterbewegung, by the spin-orbit coupling and by relativistic corrections to the electron mass ...


Search For Gravitational Waves From Low Mass Compact Binary Coalescence In 186 Days Of Ligo's Fifth Science Run, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Aug 2009

Search For Gravitational Waves From Low Mass Compact Binary Coalescence In 186 Days Of Ligo's Fifth Science Run, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

We report on a search for gravitational waves from coalescing compact binaries, of total mass between 2 and 35M, using LIGO observations between November 14, 2006 and May 18, 2007. No gravitational-wave signals were detected. We report upper limits on the rate of compact binary coalescence as a function of total mass. The LIGO cumulative 90%-confidence rate upper limits of the binary coalescence of neutron stars, black holes and black hole-neutron star systems are 1.4x10-2, 7.3x10-4 and 3.6x10yr-1L10-1, respectively, where L10 is 1010 times the blue solar ...


Three-Body Dynamics In Single Ionization Of Atomic Hydrogen By 75 Kev Proton Impact, Ahmad Hasan, Michael Schulz, Aaron C. Laforge, Jason S. Alexander, M. F. Ciappina, M. A. Khakoo, Kisra Nayomal Egodapitiya Jul 2009

Three-Body Dynamics In Single Ionization Of Atomic Hydrogen By 75 Kev Proton Impact, Ahmad Hasan, Michael Schulz, Aaron C. Laforge, Jason S. Alexander, M. F. Ciappina, M. A. Khakoo, Kisra Nayomal Egodapitiya

Physics Faculty Research & Creative Works

Doubly differential cross sections for single ionization of atomic hydrogen by 75 keV proton impact have been measured and calculated as a function of the projectile scattering angle and energy loss. This pure three-body collision system represents a fundamental test case for the study of the reaction dynamics in few-body systems. A comparison between theory and experiment reveals that three-body dynamics is important at all scattering angles and that an accurate description of the role of the projectile-target-nucleus interaction remains a major challenge to theory.


Light-Particle Single Ionization Of Argon: Influence Of The Projectile Charge Sign, Sebastian Otranto, Ronald E. Olson Jul 2009

Light-Particle Single Ionization Of Argon: Influence Of The Projectile Charge Sign, Sebastian Otranto, Ronald E. Olson

Physics Faculty Research & Creative Works

The ionization of the 3p orbital of argon by incident electrons and positrons is studied by means of the post version of the continuum distorted wave-eikonal initial-state model. Results are presented at both 200 and 500 eV impact energies for conditions amenable to present experiments. Differences in the fully differential cross sections (FDCSs) are analyzed and the influence of the projectile charge sign on the emission dynamics is discussed. The FDCSs are found to display the classic binary plus recoil peak structure at 500 eV, but transition to a more complicated four-lobed structure at the lower impact energy.


Thermal Expansion And Grüneisen Parameter In Quantum Griffiths Phases, Thomas Vojta Jul 2009

Thermal Expansion And Grüneisen Parameter In Quantum Griffiths Phases, Thomas Vojta

Physics Faculty Research & Creative Works

We consider the behavior of the Grüneisen parameter, the ratio between thermal expansion and specific heat, at pressure-tuned infinite-randomness quantum-critical points and in the associated quantum Griffiths phases. We find that the Grüneisen parameter diverges as ln (T0 /T) with vanishing temperature T in the quantum Griffiths phases. at the infinite-randomness critical point itself, the Grüneisen parameter behaves as [ln (T0 /T)]1+1/ (νψ) where ν and ψ are the correlation length and tunneling exponents. Analogous results hold for the magnetocaloric effect at magnetic-field-tuned transitions. We contrast clean and dirty systems, we discuss subtle differences between Ising ...


Accurate Retrieval Of Atomic Structures From High-Order Harmonic Spectra, Toshihito Umegaki, Toru Morishita, Shinichiro Minemoto, Yuichiro Oguchi, Anh-Thu Le, Shinichi Watanabe, Hirofumi Sakai Jul 2009

Accurate Retrieval Of Atomic Structures From High-Order Harmonic Spectra, Toshihito Umegaki, Toru Morishita, Shinichiro Minemoto, Yuichiro Oguchi, Anh-Thu Le, Shinichi Watanabe, Hirofumi Sakai

Physics Faculty Research & Creative Works

We extracted the photorecombination cross sections from the high-order harmonic spectra generated from rare gases by intense femtosecond pulses. By taking the ratio between the observed high-order harmonic spectra and recolliding electron wave packets, we successfully obtained the photorecombination cross sections.


Quantitative Rescattering Theory For High-Order Harmonic Generation From Molecules, Anh-Thu Le, R. R. Lucchese, S. Tonzani, Toru Morishita, C. D. Lin Jul 2009

Quantitative Rescattering Theory For High-Order Harmonic Generation From Molecules, Anh-Thu Le, R. R. Lucchese, S. Tonzani, Toru Morishita, C. D. Lin

Physics Faculty Research & Creative Works

The quantitative rescattering theory (QRS) for high-order harmonic generation (HHG) by intense laser pulses is presented. According to the QRS, HHG spectra can be expressed as a product of a returning electron wave packet and the photorecombination differential cross section of the laser-free continuum electron back to the initial bound state. We show that the shape of the returning electron wave packet is determined mostly by the laser. The returning electron wave packets can be obtained from the strong-field approximation or from the solution of the time-dependent Schrödinger equation (TDSE) for a reference atom. The validity of the QRS is ...


Simulations Of Baryon Acoustic Oscillations. Ii. Covariance Matrix Of The Matter Power Spectrum, Ryuichi Takahashi, Naoki Yoshida, Masahiro Takada, Takahiko Matsubara, Naoshi Sugiyama, Issha Kayo, Atsushi J. Nishizawa, Takahiro Nishimichi, Shun Saito, Atsushi Taruya Jul 2009

Simulations Of Baryon Acoustic Oscillations. Ii. Covariance Matrix Of The Matter Power Spectrum, Ryuichi Takahashi, Naoki Yoshida, Masahiro Takada, Takahiko Matsubara, Naoshi Sugiyama, Issha Kayo, Atsushi J. Nishizawa, Takahiro Nishimichi, Shun Saito, Atsushi Taruya

Physics Faculty Research & Creative Works

We use 5000 cosmological N-body simulations of 1 h-3 Gpc3 box for the concordance ËCDM model in order to study the sampling variances of a nonlinear matter power spectrum. We show that the non-Gaussian errors can be important even on large length scales relevant for baryon acoustic oscillations (BAOs). Our findings are the following: (1) the non-Gaussian errors degrade the cumulative signal-to-noise ratios (S/Ns) for the power spectrum amplitude by up to a factor of 2 and 4 for redshifts z = 1 and 0, respectively; (2) there is little information on the power spectrum amplitudes in the ...


Stacked Search For Gravitational Waves From The 2006 Sgr 1900+14 Storm, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Jul 2009

Stacked Search For Gravitational Waves From The 2006 Sgr 1900+14 Storm, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

We present the results of a LIGO search for short-duration gravitational waves (GWs) associated with the 2006 March 29 SGR 1900+14 storm. A new search method is used, "stacking" the GW data around the times of individual soft-gamma bursts in the storm to enhance sensitivity for models in which multiple bursts are accompanied by GW emission. We assume that variation in the time difference between burst electromagnetic emission and potential burst GW emission is small relative to the GW signal duration, and we time-align GW excess power time-frequency tilings containing individual burst triggers to their corresponding electromagnetic emissions. We ...


String Resonances At The Large Hadron Collider, Arunava Roy, Marco Cavaglia Jul 2009

String Resonances At The Large Hadron Collider, Arunava Roy, Marco Cavaglia

Physics Faculty Research & Creative Works

The Large Hadron Collider promises to discover new physics beyond the standard model. An exciting possibility is the formation of string resonances at the TeV scale. In this article, we show how string resonances may be detected at the LHC in the pp →γ + jet channel. Our study is based on event-shape variables, missing energy and momentum, maximum transverse momentum of photons and dijet invariant mass. These observables provide interesting signatures which enable us to discriminate string events from the standard model background.


Search For Gravitational Waves From Low Mass Binary Coalescences In The First Year Of Ligo's S5 Data, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Jun 2009

Search For Gravitational Waves From Low Mass Binary Coalescences In The First Year Of Ligo's S5 Data, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

We have searched for gravitational waves from coalescing low mass compact binary systems with a total mass between 2M and 35M and a minimum component mass of 1M using data from the first year of the fifth science run of the three LIGO detectors, operating at design sensitivity. Depending on the mass, we are sensitive to coalescences as far as 150 Mpc from the Earth. No gravitational-wave signals were observed above the expected background. Assuming a population of compact binary objects with a Gaussian mass distribution representing binary neutron star systems, black hole-neutron star binary systems, and ...


Retrieval Of Target Photorecombination Cross Sections From High-Order Harmonics Generated In A Macroscopic Medium, Cheng Jin, Anh-Thu Le, C. D. Lin May 2009

Retrieval Of Target Photorecombination Cross Sections From High-Order Harmonics Generated In A Macroscopic Medium, Cheng Jin, Anh-Thu Le, C. D. Lin

Physics Faculty Research & Creative Works

We investigate high-order harmonic generation (HHG) in a thin macroscopic medium by solving Maxwell's equation using microscopic single-atom induced dipole moment calculated from the recently developed quantitative rescattering (QRS) theory. We show that macroscopic HHG yields calculated from QRS compared well with those obtained from solving the single-atom time-dependent Schrödinger equation but with great saving of computer time. We also show that macroscopic HHG can be expressed as a product of a "macroscopic wave packet" and the photorecombination cross section of the target gas. The latter enables us to extract target structure from the experimentally measured HHG spectra, thus ...


Treatment Of Ion-Atom Collisions Using A Partial-Wave Expansion Of The Projectile Wavefunction, T. G. Wong, M. Foster, J. Colgan, Don H. Madison May 2009

Treatment Of Ion-Atom Collisions Using A Partial-Wave Expansion Of The Projectile Wavefunction, T. G. Wong, M. Foster, J. Colgan, Don H. Madison

Physics Faculty Research & Creative Works

We present calculations of ion-atom collisions using a partial-wave expansion of the projectile wavefunction. Most calculations of ion-atom collisions have typically used classical or plane-wave approximations for the projectile wavefunction, since partial-wave expansions are expected to require prohibitively large numbers of terms to converge scattering quantities. Here we show that such calculations are possible using modern high-performance computing. We demonstrate the utility of our method by examining elastic scattering of protons by hydrogen and helium atoms, problems familiar to undergraduate students of atomic scattering. Application to ionization of helium using partial-wave expansions of the projectile wavefunction, which has long been ...


Probing Molecular Frame Photoionization Via Laser Generated High-Order Harmonics From Aligned Molecules, Anh-Thu Le, R. R. Lucchese, M. T. Lee, C. D. Lin May 2009

Probing Molecular Frame Photoionization Via Laser Generated High-Order Harmonics From Aligned Molecules, Anh-Thu Le, R. R. Lucchese, M. T. Lee, C. D. Lin

Physics Faculty Research & Creative Works

Present experiments cannot measure molecular frame photoelectron angular distributions (MFPAD) for ionization from the outermost valence orbitals of molecules. We show that the details of MFPAD can be retrieved with high-order harmonics generated by infrared lasers from aligned molecules. Using accurately calculated photoionization transition dipole moments for fixed-in-space molecules, we show that the dependence of the magnitude and phase of the high-order harmonics on the alignment angle of the molecules observed in recent experiments can be quantitatively reproduced. This result provides the needed theoretical basis for ultrafast dynamic chemical imaging using infrared laser pulses.


Feasibility Of Coherent Xuv Spectroscopy On The 1s-2s Transition In Singly Ionized Helium, Maximilian Herrmann, Martin K. Haas, Ulrich D. Jentschura, Franz Kottmann, Dietrich Leibfried, Guido Saathoff, Christoph Gohle, Akira Ozawa, V. Batteiger, S. Knunz, Nikolai N. Kolachevsky, H. A. Schussler, Theodor Wolfgang Hansch, Th H. Udem May 2009

Feasibility Of Coherent Xuv Spectroscopy On The 1s-2s Transition In Singly Ionized Helium, Maximilian Herrmann, Martin K. Haas, Ulrich D. Jentschura, Franz Kottmann, Dietrich Leibfried, Guido Saathoff, Christoph Gohle, Akira Ozawa, V. Batteiger, S. Knunz, Nikolai N. Kolachevsky, H. A. Schussler, Theodor Wolfgang Hansch, Th H. Udem

Physics Faculty Research & Creative Works

The 1S-2S two-photon transition in singly ionized helium is a highly interesting candidate for precision tests of bound-state quantum electrodynamics (QED). With the recent advent of extreme ultraviolet frequency combs, highly coherent quasi-continuous-wave light sources at 61 nm have become available, and precision spectroscopy of this transition now comes into reach for the first time. We discuss quantitatively the feasibility of such an experiment by analyzing excitation and ionization rates, propose an experimental scheme, and explore the potential for QED tests.