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Articles 1 - 30 of 67

Full-Text Articles in Physical Sciences and Mathematics

Enhanced Piezoresponse And Nonlinear Optical Properties Of Fluorinated Self-Assembled Peptide Nanotubes, Soma Khanra, Sandra V. Vassiliades, Wendel A. Alves, Kaidi Yang, Rainer Glaser, Kartik Ghosh, Payal Bhattacharya, Ping Yu, Suchismita Guha Nov 2019

Enhanced Piezoresponse And Nonlinear Optical Properties Of Fluorinated Self-Assembled Peptide Nanotubes, Soma Khanra, Sandra V. Vassiliades, Wendel A. Alves, Kaidi Yang, Rainer Glaser, Kartik Ghosh, Payal Bhattacharya, Ping Yu, Suchismita Guha

Chemistry Faculty Research & Creative Works

Self-assembled L,L-diphenylalanine (FF) nanostructures offer an attractive platform for photonics and nonlinear optics. The nonlinear optical (NLO) coefficients of FF nanotubes depend on the diameter of the tube [S. Khanra et al. Phys. Chem. Chem. Phys. 19(4), 3084-3093 (2017)]. To further enhance the NLO properties of FF, we search for structural modifications. Here, we report on the synthesis of fluorinated FF dipeptides by replacing one ortho-hydrogen atom in each of the phenyl groups of FF by a fluorine atom. Density-functional theoretical calculations yield insights into minimum energy conformers of fluorinated FF (Fl-FF). Fl-FF self-assembles akin to FF into ...


Atoms In Quasilocal Integral Domains, Kevin Wilson Bombardier May 2019

Atoms In Quasilocal Integral Domains, Kevin Wilson Bombardier

Theses and Dissertations

Let R be an integral domain. An atom is a nonzero nonunit x of R where x = yz implies that either y or z is a unit. We say that R is an atomic domain if each nonzero nonunit is a finite product of atoms. An atomic domain with only finitely many nonassociate atoms is called a Cohen-Kaplansky (CK) domain. We will investigate atoms in integral domains R with a unique maximal ideal M. Of particular interest will be atoms that are not in M^2.

After studying the atoms in integral domains, we will narrow our focus to CK ...


Resonance Strengths For Kll Dielectronic Recombination Of Highly Charged Mercury Ions And Improved Empirical Z -Scaling Law, Zoltan Harman, Chintan Shah, Antonio J. Gonzalez Martinez, Ulrich D. Jentschura, For Full List Of Authors, See Publisher's Website. Jan 2019

Resonance Strengths For Kll Dielectronic Recombination Of Highly Charged Mercury Ions And Improved Empirical Z -Scaling Law, Zoltan Harman, Chintan Shah, Antonio J. Gonzalez Martinez, Ulrich D. Jentschura, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

Theoretical and experimental resonance strengths for KLL dielectronic recombination (DR) into He-, Li-, Be-, and B-like mercury ions are presented, based on state-resolved DR x-ray spectra recorded at the Heidelberg electron-beam ion trap. The DR resonance strengths are experimentally extracted by normalizing them to simultaneously recorded radiative recombination signals. The results are compared to state-of-the-art atomic calculations that include relativistic electron correlation and configuration mixing effects. Combining the present data with other existing ones, we derive an improved semiempirical Z-scaling law for DR resonance strengths as a function of the atomic number, taking into account higher-order relativistic corrections, which are ...


All-Optical Atom Trap As A Target For Motrims-Like Collision Experiments, S. Sharma, B. P. Acharya, Daniel Fischer, For Full List Of Authors, See Publisher's Website. Apr 2018

All-Optical Atom Trap As A Target For Motrims-Like Collision Experiments, S. Sharma, B. P. Acharya, Daniel Fischer, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

Momentum-resolved scattering experiments with laser-cooled atomic targets have been performed since almost two decades with magneto-optical trap recoil ion momentum spectroscopy (MOTRIMS) setups. Compared to experiments with gas-jet targets, MOTRIMS features significantly lower target temperatures allowing for an excellent recoil ion momentum resolution. However, the coincident and momentum-resolved detection of electrons was long rendered impossible due to incompatible magnetic field requirements. Here we report on an experimental approach which is based on an all-optical 6Liatom trap that--in contrast to magneto-optical traps--does not require magnetic field gradients in the trapping region. Atom temperatures of about 2 mK and number densities ...


Long-Range Interactions Of Hydrogen Atoms In Excited States. Iii. Ns−1s Interactions For N ≥ 3, Chandra M. Adhikari, V. Debierre, Ulrich D. Jentschura Sep 2017

Long-Range Interactions Of Hydrogen Atoms In Excited States. Iii. Ns−1s Interactions For N ≥ 3, Chandra M. Adhikari, V. Debierre, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

The long-range interaction of excited neutral atoms has a number of interesting and surprising properties such as the prevalence of long-range oscillatory tails and the emergence of numerically large van der Waals C6 coefficients. Furthermore, the energetically quasidegenerate nP states require special attention and lead to mathematical subtleties. Here we analyze the interaction of excited hydrogen atoms in nS states (3 ≤ n ≤ 12) with ground-state hydrogen atoms and find that the C6 coefficients roughly grow with the fourth power of the principal quantum number and can reach values in excess of 240000 (in atomic units) for states with n ...


Electron-Impact Ionization Of Laser-Aligned Atoms -- Contributions From Both Natural And Unnatural-Parity States, Andrew James Murray, James Colgan, Don H. Madison, Matthew Harvey, Ahmad Sakaamini Aug 2017

Electron-Impact Ionization Of Laser-Aligned Atoms -- Contributions From Both Natural And Unnatural-Parity States, Andrew James Murray, James Colgan, Don H. Madison, Matthew Harvey, Ahmad Sakaamini

Physics Faculty Research & Creative Works

Synopsis. The progress of experimental and theoretical measurements for (e,2e) ionization cross sections from laser-aligned atoms is presented here. It is found that both natural and unnatural parity contributions must be included in the models to emulate the experimental data.


Natural & Unnatural-Parity Contributions In Electron-Impact Ionization Of Laser-Aligned Atoms, Andrew James Murray, James Colgan, Don H. Madison, Matthew Harvey, Ahmad Sakaamini, James Pursehouse, Kate Nixon, Al Stauffer Aug 2017

Natural & Unnatural-Parity Contributions In Electron-Impact Ionization Of Laser-Aligned Atoms, Andrew James Murray, James Colgan, Don H. Madison, Matthew Harvey, Ahmad Sakaamini, James Pursehouse, Kate Nixon, Al Stauffer

Physics Faculty Research & Creative Works

Differential cross section measurements from laser-aligned Mg atoms are compared to theoretical calculations using both time dependent and time-independent formalisms. It is found that both natural and unnatural parity contributions to the calculated cross sections are required to emulate the data when the state is aligned out of the scattering plane.


Long-Range Tails In Van Der Waals Interactions Of Excited-State And Ground-State Atoms, Ulrich D. Jentschura, V. Debierre Apr 2017

Long-Range Tails In Van Der Waals Interactions Of Excited-State And Ground-State Atoms, Ulrich D. Jentschura, V. Debierre

Physics Faculty Research & Creative Works

A quantum electrodynamic calculation of the interaction of an excited-state atom with a ground-state atom is performed. For an excited reference state and a lower-lying virtual state, the contribution to the interaction energy naturally splits into a pole term and a Wick-rotated term. The pole term is shown to dominate in the long-range limit, altering the functional form of the interaction from the retarded 1/R7 Casimir-Polder form to a long-range tail - provided by the Wick-rotated term - proportional to cos[2(Em - En)R/(ħc)]/R2, where Em < En is the energy of a virtual ...


Virtual Resonant Emission And Oscillatory Long-Range Tails In Van Der Waals Interactions Of Excited States: Qedtreatment And Applications, Ulrich D. Jentschura, Chandra Mani Adhikari, Vincent Debierre Mar 2017

Virtual Resonant Emission And Oscillatory Long-Range Tails In Van Der Waals Interactions Of Excited States: Qedtreatment And Applications, Ulrich D. Jentschura, Chandra Mani Adhikari, Vincent Debierre

Physics Faculty Research & Creative Works

We report on a quantum electrodynamic (QED) investigation of the interaction between a ground state atom with another atom in an excited state. General expressions, applicable to any atom, are indicated for the long-range tails that are due to virtual resonant emission and absorption into and from vacuum modes whose frequency equals the transition frequency to available lower-lying atomic states. For identical atoms, one of which is in an excited state, we also discuss the mixing term that depends on the symmetry of the two-atom wave function (these evolve into either the gerade or the ungerade state for close approach ...


Long-Range Interactions Of Hydrogen Atoms In Excited States. Ii. Hyperfine-Resolved 2s-2s Systems, Ulrich D. Jentschura, Vincent Debierre, Chandra Mani Adhikari, Arthur N. Matveev, Nikolai N. Kolachevsky Feb 2017

Long-Range Interactions Of Hydrogen Atoms In Excited States. Ii. Hyperfine-Resolved 2s-2s Systems, Ulrich D. Jentschura, Vincent Debierre, Chandra Mani Adhikari, Arthur N. Matveev, Nikolai N. Kolachevsky

Physics Faculty Research & Creative Works

The interaction of two excited hydrogen atoms in metastable states constitutes a theoretically interesting problem because of the quasidegenerate 2P1/2 levels that are removed from the 2S states only by the Lamb shift. The total Hamiltonian of the system is composed of the van der Waals Hamiltonian, the Lamb shift, and the hyperfine effects. The van der Waals shift becomes commensurate with the 2S-2P3/2 fine-structure splitting only for close approach (R < 100a0, where a0 is the Bohr radius) and one may thus restrict the discussion to the levels with n = 2 and J = 1/2 ...


Long-Range Interactions Of Hydrogen Atoms In Excited States. I. 2s-1s Interactions And Dirac-Δ Perturbations, Chandra Mani Adhikari, Vincent Debierre, Arthur N. Matveev, Nikolai N. Kolachevsky, Ulrich D. Jentschura Feb 2017

Long-Range Interactions Of Hydrogen Atoms In Excited States. I. 2s-1s Interactions And Dirac-Δ Perturbations, Chandra Mani Adhikari, Vincent Debierre, Arthur N. Matveev, Nikolai N. Kolachevsky, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

The theory of the long-range interaction of metastable excited atomic states with ground-state atoms is analyzed. We show that the long-range interaction is essentially modified when quasidegenerate states are available for virtual transitions. A discrepancy in the literature regarding the van der Waals coefficient C6 (2S ;1 S ) describing the interaction of metastable atomic hydrogen ( 2 S state) with a ground-state hydrogen atom is resolved. In the the van der Waals range a0 ≪ R ≪ a0 / α , where a0 = ℏ / α m c is the Bohr radius and α is the fine-structure constant, one finds the symmetry-dependent result ...


Determination Of Interstellar O Parameters Using The First Two Years Of Data From The Interstellar Boundary Explorer, N. A. Schwadron, E. Möbius, D. J. Mccomas, P. Bochsler, M. Bzowski, S. A. Fuselier, G. Livadiotis, P. Frisch, H. R. Müller, D. Heirtzler, H. Kucharek, M. A. Lee Sep 2016

Determination Of Interstellar O Parameters Using The First Two Years Of Data From The Interstellar Boundary Explorer, N. A. Schwadron, E. Möbius, D. J. Mccomas, P. Bochsler, M. Bzowski, S. A. Fuselier, G. Livadiotis, P. Frisch, H. R. Müller, D. Heirtzler, H. Kucharek, M. A. Lee

Open Dartmouth: Peer-reviewed articles by Dartmouth faculty

The direct measurements of interstellar matter by the Interstellar Boundary Explorer ( IBEX ) mission have opened a new and important chapter in our study of the interactions that control the boundaries of our heliosphere. Here we derive for the quantitative information about interstellar O flow parameters from IBEX low-energy neutral atom data for the first time. Specifically, we derive a relatively narrow four-dimensional parameter tube along which interstellar O flow parameters must lie. Along the parameter tube, we find a large uncertainty in interstellar O flow longitude, 76°.0 ± 3°.4 from χ 2 analysis and 76°.5 ± 6°.2 from ...


Theory Of Noncontact Friction For Atom-Surface Interactions, Ulrich D. Jentschura, M. Janke, Maarten F M De Kieviet Aug 2016

Theory Of Noncontact Friction For Atom-Surface Interactions, Ulrich D. Jentschura, M. Janke, Maarten F M De Kieviet

Physics Faculty Research & Creative Works

The noncontact (van der Waals) friction is an interesting physical effect, which has been the subject of controversial scientific discussion. The direct friction term due to the thermal fluctuations of the electromagnetic field leads to a friction force proportional to 1/Z5 (where Z is the atom-wall distance). The backaction friction term takes into account the feedback of thermal fluctuations of the atomic dipole moment onto the motion of the atom and scales as 1/Z8. We investigate noncontact friction effects for the interactions of hydrogen, ground-state helium, and metastable helium atoms with α-quartz (SiO2), gold (Au ...


Analytical Model For Calibrating Laser Intensity In Strong-Field-Ionization Experiments, Song-Feng. Zhao, Anh-Thu Le, Cheng Jin, Xu Wang, C. D. Lin Feb 2016

Analytical Model For Calibrating Laser Intensity In Strong-Field-Ionization Experiments, Song-Feng. Zhao, Anh-Thu Le, Cheng Jin, Xu Wang, C. D. Lin

Physics Faculty Research & Creative Works

The interaction of an intense laser pulse with atoms and molecules depends extremely nonlinearly on the laser intensity. Yet experimentally there still exists no simple reliable methods for determining the peak laser intensity within the focused volume. Here we present a simple method, based on an improved Perelomov-Popov-Terent'ev model, that would allow the calibration of laser intensities from the measured ionization signals of atoms or molecules. The model is first examined by comparing ionization probabilities (or signals) of atoms and several simple diatomic molecules with those from solving the time-dependent Schrödinger equation. We then show the possibility of using ...


Few-Boson Processes In The Presence Of An Attractive Impurity Under One-Dimensional Confinement, Nirav Mehta, Connor Morehead Nov 2015

Few-Boson Processes In The Presence Of An Attractive Impurity Under One-Dimensional Confinement, Nirav Mehta, Connor Morehead

Nirav P Mehta

We consider a few-boson system confined to one dimension with a single distinguishable particle of lesser mass. All particle interactions are modeled with δ functions, but due to the mass imbalance the problem is nonintegrable. Universal few-body binding energies, atom-dimer and atom-trimer scattering lengths, are all calculated in terms of two parameters, namely the mass ratio mL/mH, and ratio gHH/gHL of the δ-function couplings. We specifically identify the values of these ratios for which the atom-dimer or atom-trimer scattering lengths vanish or diverge. We identify regions in this parameter space in which various few-body inelastic processes become energetically ...


Energy-Efficient Computational Chemistry: Comparison Of X86 And Arm Systems, Kristopher Keipert, Gaurav Mitra, Vaibhav Sunriyal, Sarom S. Leang, Masha Sosonkina, Alistair P. Rendell, Mark S. Gordon Nov 2015

Energy-Efficient Computational Chemistry: Comparison Of X86 And Arm Systems, Kristopher Keipert, Gaurav Mitra, Vaibhav Sunriyal, Sarom S. Leang, Masha Sosonkina, Alistair P. Rendell, Mark S. Gordon

Computational Modeling and Simulation Engineering Faculty Publications

The computational efficiency and energy-to-solution of several applications using the GAMESS quantum chemistry suite of codes is evaluated for 32-bit and 64-bit ARM-based computers, and compared to an x86 machine. The x86 system completes all benchmark computations more quickly than either ARM system and is the best choice to minimize time to solution. The ARM64 and ARM32 computational performances are similar to each other for Hartree-Fock and density functional theory energy calculations. However, for memory-intensive second-order perturbation theory energy and gradient computations the lower ARM32 read/write memory bandwidth results in computation times as much as 86% longer than on ...


Few-Boson Processes In The Presence Of An Attractive Impurity Under One-Dimensional Confinement, Nirav P. Mehta, Connor D. Morehead Oct 2015

Few-Boson Processes In The Presence Of An Attractive Impurity Under One-Dimensional Confinement, Nirav P. Mehta, Connor D. Morehead

Physics and Astronomy Faculty Research

We consider a few-boson system confined to one dimension with a single distinguishable particle of lesser mass. All particle interactions are modeled with δ functions, but due to the mass imbalance the problem is nonintegrable. Universal few-body binding energies, atom-dimer and atom-trimer scattering lengths, are all calculated in terms of two parameters, namely the mass ratio mL/mH, and ratio gHH/gHL of the δ-function couplings. We specifically identify the values of these ratios for which the atom-dimer or atom-trimer scattering lengths vanish or diverge. We identify regions in this parameter space in which various ...


Exploring The Possibility Of O And Ne Contamination In Ulysses Observations Of Interstellar Helium, Brian E. Wood, Hans-Reinhard Müller, Maciej Bzowski, Justyna M. Sokół Oct 2015

Exploring The Possibility Of O And Ne Contamination In Ulysses Observations Of Interstellar Helium, Brian E. Wood, Hans-Reinhard Müller, Maciej Bzowski, Justyna M. Sokół

Open Dartmouth: Peer-reviewed articles by Dartmouth faculty

We explore the possibility that interstellar O and Ne may be contributing to the particle signal from the GAS instrument on Ulysses, which is generally assumed to be entirely He. Motivating this study is the recognition that an interstellar temperature higher than any previously estimated from Ulysses data could potentially resolve a discrepancy between Ulysses He measurements and those from the Interstellar Boundary Explorer (IBEX). Contamination by O and Ne could lead to Ulysses temperature measurements that are too low. We estimate the degree of O and Ne contamination necessary to increase the inferred Ulysses temperature to 8500 K, which ...


Low-Energy (E₀ = 65 Ev) Electron-Impact Ionization Of Neon: Internormalized Triple-Differentical Cross Sections In 3d Kinematics, Xueguang Ren, Sadek M. Amami, Oleg I. Zatsarinny, Thomas Pfluger, Marvin Weyland, Woon Yong Baek, Hans Rabus, Klaus Bartschat, Don H. Madison, Alexander Dorn Sep 2015

Low-Energy (E₀ = 65 Ev) Electron-Impact Ionization Of Neon: Internormalized Triple-Differentical Cross Sections In 3d Kinematics, Xueguang Ren, Sadek M. Amami, Oleg I. Zatsarinny, Thomas Pfluger, Marvin Weyland, Woon Yong Baek, Hans Rabus, Klaus Bartschat, Don H. Madison, Alexander Dorn

Physics Faculty Research & Creative Works

We present a combined experimental and theoretical study on the low-energy (E0 = 65 eV) electron- impact ionization of neon. The experimental data are compared to predictions from a hybrid second-order distorted-wave Born plus R-matrix approach (DWB2-RM), the distorted-wave Born approximation with inclusion of post-collision interaction (DWBA-PCI), a three-body distorted-wave approach (3DW), and a B-spline R-matrix (BSR) with pseudostates approach. Excellent agreement is found between experiment and the 3DW and BSR theories. The importance of PCI effects is clearly visible in this low-energy electron-impact ionization process.


Evidence For Unnatural-Parity Contributions To Electron-Impact Ionization Of Laser-Aligned Atoms, G. S. J. Armstrong, J. Colgan, M. S. Pindzola, S. Amami, Don H. Madison, J. Pursehouse, K. L. Nixon, A. J. Murray Sep 2015

Evidence For Unnatural-Parity Contributions To Electron-Impact Ionization Of Laser-Aligned Atoms, G. S. J. Armstrong, J. Colgan, M. S. Pindzola, S. Amami, Don H. Madison, J. Pursehouse, K. L. Nixon, A. J. Murray

Physics Faculty Research & Creative Works

Recent measurements have examined the electron-impact ionization of excited-state laser-aligned Mg atoms. In this work we show that the ionization cross section arising from the geometry where the aligned atom is perpendicular to the scattering plane directly probes the unnatural parity contributions to the ionization amplitude. The contributions from natural parity partial waves cancel exactly in this geometry. Our calculations resolve the discrepancy between the nonzero measured cross sections in this plane and the zero cross section predicted by distorted-wave approaches. We demonstrate that this is a general feature of ionization from p-state targets by additional studies of ionization from ...


Coplanar Asymmetric Angles And Symmetric Energy Sharing Triple Differential Cross Sections For 200 Ev Electron-Impact Ionization Of Ar (3p), Zehra Nur Ozer, Sadek M. Amami, Onur Varol, Murat Yavuz, Mevlut Dogan, Don H. Madison Sep 2015

Coplanar Asymmetric Angles And Symmetric Energy Sharing Triple Differential Cross Sections For 200 Ev Electron-Impact Ionization Of Ar (3p), Zehra Nur Ozer, Sadek M. Amami, Onur Varol, Murat Yavuz, Mevlut Dogan, Don H. Madison

Physics Faculty Research & Creative Works

We have measured triple differential cross sections (TDCSs) for electron-impact ionization of the 3p shell of Ar at 200 eV incident electron energy. The experiments have been performed in coplanar asymmetric energy sharing geometry. The experimental results are compared with the theoretical models of three body distorted wave (3DW) and distorted wave Born approximation (DWBA).


Revisiting Ulysses Observations Of Interstellar Helium, Brian E. Wood, Hans-Reinhard Müller, Manfred Witte Mar 2015

Revisiting Ulysses Observations Of Interstellar Helium, Brian E. Wood, Hans-Reinhard Müller, Manfred Witte

Open Dartmouth: Peer-reviewed articles by Dartmouth faculty

We report the results of a comprehensive reanalysis of Ulysses observations of interstellar He atoms flowing through the solar system, the goal being to reassess the interstellar He flow vector and to search for evidence of variability in this vector. We find no evidence that the He beam seen by Ulysses changes at all from 1994-2007. The direction of flow changes by no more than ~03 and the speed by no more than ~0.3 km s–1. A global fit to all acceptable He beam maps from 1994-2007 yields the following He flow parameters: V ISM = 26.08 ± 0 ...


Self-Organization Of S Adatoms On Au(111): √3r30° Rows At Low Coverage, Holly L. Walen, Da-Jiang Liu, Junepyo Oh, Hyunseob Lim, James W. Evans, Yousoo Kim, Patricia A. Thiel Jan 2015

Self-Organization Of S Adatoms On Au(111): √3r30° Rows At Low Coverage, Holly L. Walen, Da-Jiang Liu, Junepyo Oh, Hyunseob Lim, James W. Evans, Yousoo Kim, Patricia A. Thiel

Chemistry Publications

Using scanning tunneling microscopy, we observe an adlayer structure that is dominated by short rows of S atoms, on unreconstructed regions of a Au(111) surface. This structure forms upon adsorption of low S coverage (less than 0.1 monolayer) on a fully reconstructed clean surface at 300 K, then cooling to 5 K for observation. The rows adopt one of three orientations that are rotated by 30◦ from the close-packed directions of the Au(111) substrate, and adjacent S atoms in the rows are separated by √ 3 times the surface lattice constant, a. Monte Carlo simulations are performed on ...


Long-Range Displacive Reconstruction Of Au(110) Triggered By Low Coverage Of Sulfur, Holly L. Walen, Da-Jiang Liu, Junepyo Oh, Yousoo Kim, Patricia A. Thiel Jan 2015

Long-Range Displacive Reconstruction Of Au(110) Triggered By Low Coverage Of Sulfur, Holly L. Walen, Da-Jiang Liu, Junepyo Oh, Yousoo Kim, Patricia A. Thiel

Chemistry Publications

We propose a new model for the c(4 × 2) phase of sulfur adsorbed on Au(110). This is a reconstruction achieved by short-range rearrangements of Au atoms that create a pseudo-4-fold-hollow (p4fh) site for adsorbed sulfur. The model is based partly upon the agreement between experimental STM images and those predicted from DFT, both within c(4 × 2) domains and at a boundary between two domains. It is also based on the stability of this structure in DFT, where it is not only favored over the chemisorbed phase at its ideal coverage of 0.25 ML, but also at ...


One-Loop Dominance In The Imaginary Part Of The Polarizability: Application To Blackbody And Noncontact Van Der Waals Friction, Ulrich D. Jentschura, Grzegorz Lach, Maarten Dekieviet, Krzysztof Pachucki Jan 2015

One-Loop Dominance In The Imaginary Part Of The Polarizability: Application To Blackbody And Noncontact Van Der Waals Friction, Ulrich D. Jentschura, Grzegorz Lach, Maarten Dekieviet, Krzysztof Pachucki

Physics Faculty Research & Creative Works

Phenomenologically important quantum dissipative processes include blackbody friction (an atom absorbs counterpropagating blueshifted photons and spontaneously emits them in all directions, losing kinetic energy) and noncontact van der Waals friction (in the vicinity of a dielectric surface, the mirror charges of the constituent particles inside the surface experience drag, slowing the atom). The theoretical predictions for these processes are modified upon a rigorous quantum electrodynamic treatment, which shows that the one-loop "correction" yields the dominant contribution to the off-resonant, gauge-invariant, imaginary part of the atom's polarizability at room temperature, for typical atom-surface interactions. The tree-level contribution to the polarizability ...


Long-Range Atom-Wall Interactions And Mixing Terms: Metastable Hydrogen, Ulrich D. Jentschura Jan 2015

Long-Range Atom-Wall Interactions And Mixing Terms: Metastable Hydrogen, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

We investigate the interaction of metastable 2S hydrogen atoms with a perfectly conducting wall, including parity-breaking S-P mixing terms (with full account of retardation). The neighboring 2P1/2 and 2P3/2 levels are found to have a profound effect on the transition from the short-range, nonrelativistic regime, to the retarded form of the Casimir-Polder interaction. The corresponding P state admixtures to the metastable 2S state are calculated. We find the long-range asymptotics of the retarded Casimir-Polder potentials and mixing amplitudes for general excited states, including a fully quantum electrodynamic treatment of the dipole-quadrupole mixing term. The decay width ...


Fine-Structure Constant For Gravitational And Scalar Interactions, Ulrich D. Jentschura Aug 2014

Fine-Structure Constant For Gravitational And Scalar Interactions, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

Starting from the coupling of a relativistic quantum particle to the curved Schwarzschild space time, we show that the Dirac-Schwarzschild problem has bound states and calculate their energies including relativistic corrections. Relativistic effects are shown to be suppressed by the gravitational fine-structure constant αG=Gm1m2/(ℏc), where G is Newton's gravitational constant, c is the speed of light, and m1 and m2 ≫ m1 are the masses of the two particles. The kinetic corrections due to space-time curvature are shown to lift the familiar (n,j) degeneracy of the energy levels of the ...


Effect Of The Center-Of-Mass Approximation On The Scaling Of Electron-Capture Fully Differential Cross Sections, A. L. Harris, Don H. Madison Aug 2014

Effect Of The Center-Of-Mass Approximation On The Scaling Of Electron-Capture Fully Differential Cross Sections, A. L. Harris, Don H. Madison

Physics Faculty Research & Creative Works

We present results for p+He single electron capture and transfer with target excitation using the first Born approximation. The effect of approximating the center of mass of the helium atom and outgoing hydrogen atom at the respective nuclei is explored. Semianalytical results are compared for the calculations with and without the approximation, and it is shown that one must properly account for the center of mass of the atoms. It is also shown that this approximation is the result of the apparent v4 scaling that was previously observed with the four-body transfer with target excitation model.


Theoretical And Experimental Investigation Of (E, 2e) Ionization Of Argon 3p In Asymmetric Kinematics At Intermediate Energy, Sadek Amami, Melike Ulu, Zehra Nur Ozer, Murat Yavuz, Suay Kazgoz, Mevlut Dogan, Oleg Zatsarinny, Klaus Bartschat, Don H. Madison Jul 2014

Theoretical And Experimental Investigation Of (E, 2e) Ionization Of Argon 3p In Asymmetric Kinematics At Intermediate Energy, Sadek Amami, Melike Ulu, Zehra Nur Ozer, Murat Yavuz, Suay Kazgoz, Mevlut Dogan, Oleg Zatsarinny, Klaus Bartschat, Don H. Madison

Physics Faculty Research & Creative Works

The field of electron-impact ionization of atoms, or (e, 2e), has provided significant detailed information about the physics of collisions. For ionization of hydrogen and helium, essentially exact numerical methods have been developed which can correctly predict what will happen. For larger atoms, we do not have theories of comparable accuracy. Considerable attention has been given to ionization of inert gases and, of the inert gases, argon seems to be the most difficult target for theory. There have been several studies comparing experiment and perturbative theoretical approaches over the last few decades, and generally qualitative but not quantitative agreement is ...


Born-Oppenheimer Study Of Two-Component Few-Particle Systems Under One-Dimensional Confinement, Nirav P. Mehta May 2014

Born-Oppenheimer Study Of Two-Component Few-Particle Systems Under One-Dimensional Confinement, Nirav P. Mehta

Physics and Astronomy Faculty Research

The energy spectrum, atom-dimer scattering length, and atom-trimer scattering length for systems of three and four ultracold atoms with δ-function interactions in one dimension are presented as a function of the relative mass ratio of the interacting atoms. The Born-Oppenheimer approach is used to treat three-body (“HHL”) systems of one light and two heavy atoms, as well as four-body (“HHHL”) systems of one light and three heavy atoms. Zero-range interactions of arbitrary strength are assumed between different atoms, but the heavy atoms are assumed to be noninteracting among themselves. Fermionic and bosonic heavy atoms with both positive and negative parity ...