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Articles 1 - 22 of 22
Full-Text Articles in Physical Sciences and Mathematics
Exploring The X-Ray Universe In The Microcalorimeter Era, Priyanka Chakraborty
Exploring The X-Ray Universe In The Microcalorimeter Era, Priyanka Chakraborty
Theses and Dissertations--Physics and Astronomy
Next-generation microcalorimeter missions like XRISM and Athena will revolutionize X-ray spectroscopy by offering a plethora of high-resolution X-ray spectra. Interpreting these observations requires a complete understanding of how matter interacts with light through such microphysical processes as absorption and excitation. I developed a framework describing the atomic processes for both collisionally-ionized and photoionized plasmas over a wide range of column densities. Through various line-intensity and line-ratio spectral diagnostics, I established four asymptotic limits; Cases A, B, C, and D. These apply to the formation of lines in H- and He-like systems. This is the first work describing these limits in …
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
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 …
Control Of Energy Density Inside A Disordered Medium By Coupling To Open Or Closed Channels, Raktim Sarma, Alexey Yamilov, Sasha Petrenko, Yaron Bromberg, Hui Cao
Control Of Energy Density Inside A Disordered Medium By Coupling To Open Or Closed Channels, Raktim Sarma, Alexey Yamilov, Sasha Petrenko, Yaron Bromberg, Hui Cao
Physics Faculty Research & Creative Works
We demonstrate experimentally the efficient control of light intensity distribution inside a random scattering system. The adaptive wave front shaping technique is applied to a silicon waveguide containing scattering nanostructures, and the on-chip coupling scheme enables access to all input spatial modes. By selectively coupling the incident light to the open or closed channels of the disordered system, we not only vary the total energy stored inside the system by a factor of 7.4, but also change the energy density distribution from an exponential decay to a linear decay and to a profile peaked near the center. This work provides …
Muonic Bound Systems, Virtual Particles, And Proton Radius, Ulrich D. Jentschura
Muonic Bound Systems, Virtual Particles, And Proton Radius, Ulrich D. Jentschura
Physics Faculty Research & Creative Works
The proton radius puzzle questions the self-consistency of theory and experiment in light muonic and electronic bound systems. Here we summarize the current status of virtual particle models as well as Lorentz-violating models that have been proposed in order to explain the discrepancy. Highly charged one-electron ions and muonic bound systems have been used as probes of the strongest electromagnetic fields achievable in the laboratory. The average electric field seen by a muon orbiting a proton is comparable to hydrogenlike uranium and, notably, larger than the electric field in the most advanced strong-laser facilities. Effective interactions due to virtual annihilation …
Theoretical And Experimental (E, 2e) Study Of Electron-Impact Ionization Of Laser-Aligned Mg Atoms, Sadek Amami, Andrew J. Murray, Al Stauffer, Kate Nixon, Gregory Armstrong, James Colgan, Don H. Madison
Theoretical And Experimental (E, 2e) Study Of Electron-Impact Ionization Of Laser-Aligned Mg Atoms, Sadek Amami, Andrew J. Murray, Al Stauffer, Kate Nixon, Gregory Armstrong, James Colgan, Don H. Madison
Physics Faculty Research & Creative Works
We have performed calculations of the fully differential cross sections for electron-impact ionization of magnesium atoms. Three theoretical approximations, the time-dependent close coupling, the three-body distorted wave, and the distorted wave Born approximation, are compared with experiment in this article. Results will be shown for ionization of the 3s ground state of Mg for both asymmetric and symmetric coplanar geometries. Results will also be shown for ionization of the 3p state which has been excited by a linearly polarized laser which produces a charge cloud aligned perpendicular to the laser beam direction and parallel to the linear polarization. Theoretical and …
780 Nm Diode Lasers For Atomic Physics, Bryson Vivas, Simone Carpenter, Jenny Novak, Andrew M. C. Dawes
780 Nm Diode Lasers For Atomic Physics, Bryson Vivas, Simone Carpenter, Jenny Novak, Andrew M. C. Dawes
Andrew M C Dawes
This poster presents the results of the summer research project conducted by Bryson Vivas, Simone Carpenter, and Jenny Novak. The research was supervised by Dr. Andrew Dawes and conducted in the Photonics and Quantum Optics Lab of Pacific University.
Numerical Simulations Of Chirped Excitation, Benjamin Iannitelli
Numerical Simulations Of Chirped Excitation, Benjamin Iannitelli
Honors Scholar Theses
In this project I developed a general method of finding the optimal laser excitation for an ensemble of two-level atoms with the primary goal of exciting as many atoms as possible, as quickly as possible, for as long as possible, in order of decreasing priority. Specifically, I simulated the laser excitation of a collection of Rubidium-87 atoms from (n=5, L=0, S=1/2, J=1/2) to (n=5, L=1, S=1/2, J=3/2), by finding numerical solutions to the optical Bloch equations. I optimized the parameters of a linear chirp paired with a Gaussian intensity pulse first neglecting and then including spontaneous emission, and then for …
Essentials Of The Theory Of Abstraction - Lecture, Subhajit Kumar Ganguly
Essentials Of The Theory Of Abstraction - Lecture, Subhajit Kumar Ganguly
Subhajit Kumar Ganguly
In not favouring solutions or sets of solutions, the principle of zero-postulation drives away any unwanted incompleteness from the description of the world. It is the interactions between the possible exhaustive set of solutions that creates the impression pointedness or directiveness in the universe, leading to the formation of clusters, as discussed earlier. These interactions may be chaotic in nature, giving rise to attractor points where the directiveness inside any given system asymptotically seem to approach. It is this directiveness, in turn, inside a given system or in the universe as a whole, that is the cause of all known …
Condensation States And Landscaping With The Theory Of Abstraction, Subhajit Kumar Ganguly
Condensation States And Landscaping With The Theory Of Abstraction, Subhajit Kumar Ganguly
Subhajit Kumar Ganguly
The Abstraction theory is applied in landscaping. A collection of objects may be made to be vast or meager depending upon the scale of observations. This idea may be developed to unite the worlds of the great vastness of the universe and the minuteness of the sub-atomic realm. Keeping constant a scaling ratio for both worlds, these may actually be converted into two self-same representatives with respect to scaling. The Laws of Physical Transactions are made use of to study Bose-Einstein condensation. As the packing density of concerned constituents increase to a certain critical value, there may be evolution of …
Treatment Of Ion-Atom Collisions Using A Partial-Wave Expansion Of The Projectile Wavefunction, T. G. Wong, M. Foster, J. Colgan, Don H. Madison
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 …
Quantitative Rescattering Theory For Nonsequential Double Ionization Of Atoms By Intense Laser Pulses, Samuel Micheau, Zhangjin Chen, Anh-Thu Le, C. D. Lin
Quantitative Rescattering Theory For Nonsequential Double Ionization Of Atoms By Intense Laser Pulses, Samuel Micheau, Zhangjin Chen, Anh-Thu Le, C. D. Lin
Physics Faculty Research & Creative Works
Laser-induced electron recollisions are fundamental to many strong field phenomena in atoms and molecules. Using the recently developed quantitative rescattering theory, we demonstrate that the nonsequential double ionization (NSDI) of atoms by lasers can be obtained quantitatively in terms of inelastic collisions of the target ions with the free returning electrons where the latter are explicitly given by a spectrum-characterized wave packet. Using argon atoms as target, we calculated the NSDI yield including contributions from direct (e,2e) electron-impact ionization and electron-impact excitation accompanied by subsequent field ionization. We further investigate the dependence of total NSDI on the carrier-envelope phase of …
Retrieving Photorecombination Cross Sections Of Atoms From High-Order Harmonic Spectra, Shinichiro Minemoto, Toshihito Umegaki, Yuichiro Oguchi, Toru Morishita, Anh-Thu Le, Shinichi Watanabe, Hirofumi Sakai
Retrieving Photorecombination Cross Sections Of Atoms From High-Order Harmonic Spectra, Shinichiro Minemoto, Toshihito Umegaki, Yuichiro Oguchi, Toru Morishita, Anh-Thu Le, Shinichi Watanabe, Hirofumi Sakai
Physics Faculty Research & Creative Works
We observe high-order harmonic spectra generated from a thin atomic medium, Ar, Kr, and Xe, by intense 800-nm and 1300-nm femtosecond pulses. A clear signature of a single-atom response is observed in the harmonic spectra. Especially in the case of Ar, a Cooper minimum, reflecting the electronic structure of the atom, is observed in the harmonic spectra. We successfully extract the photorecombination cross sections of the atoms in the field-free condition with the help of an accurate recolliding electron wave packet. The present protocol paves the way for exploring ultrafast imaging of molecular dynamics with attosecond resolution.
Reexamining Blackbody Shifts For Hydrogenlike Ions, Ulrich D. Jentschura, Martin K. Haas
Reexamining Blackbody Shifts For Hydrogenlike Ions, Ulrich D. Jentschura, Martin K. Haas
Physics Faculty Research & Creative Works
We investigate blackbody-induced energy shifts for low-lying levels of atomic systems, with a special emphasis on transitions used in current and planned high-precision experiments on atomic hydrogen and ionized helium. Fine-structure- and Lamb-shift-induced blackbody shifts are found to increase with the square of the nuclear charge number, whereas blackbody shifts due to virtual transitions decrease with increasing nuclear charge as the fourth power of the nuclear charge. We also investigate the decay width acquired by the ground state of atomic hydrogen, due to interaction with blackbody photons. The corresponding width is due to an instability against excitation to higher excited …
Evidence Of Wave-Particle Duality For Single Fast Hydrogen Atoms, Henning T. Schmidt, Daniel Fischer, Zoltan Berenyi, C. Lewis Cocke, M. Gudmundsson, Nicole Haag, Henrik A B Johansson, Anders Kallberg, Sergey B. Levin, Peter Reinhed, Ulf Sassenberg, Reinhold S. Schuch, Ansgar Simonsson, Kristian Stochkel, Henrik Cederquist
Evidence Of Wave-Particle Duality For Single Fast Hydrogen Atoms, Henning T. Schmidt, Daniel Fischer, Zoltan Berenyi, C. Lewis Cocke, M. Gudmundsson, Nicole Haag, Henrik A B Johansson, Anders Kallberg, Sergey B. Levin, Peter Reinhed, Ulf Sassenberg, Reinhold S. Schuch, Ansgar Simonsson, Kristian Stochkel, Henrik Cederquist
Physics Faculty Research & Creative Works
We report the direct observation of interference effects in a Young's double-slit experiment where the interfering waves are two spatially separated components of the de Broglie wave of single 1.3 MeV hydrogen atoms formed close to either target nucleus in H++H2 electron-transfer collisions. Quantum interference strongly influences the results even though the hydrogen atoms have a de Broglie wavelength, λdB, as small as 25 fm.
Extraction Of The Species-Dependent Dipole Amplitude And Phase From High-Order Harmonic Spectra In Rare-Gas Atoms, Anh-Thu Le, Toru Morishita, C. D. Lin
Extraction Of The Species-Dependent Dipole Amplitude And Phase From High-Order Harmonic Spectra In Rare-Gas Atoms, Anh-Thu Le, Toru Morishita, C. D. Lin
Physics Faculty Research & Creative Works
Based on high-order harmonic generation (HHG) spectra obtained from solving the time-dependent Schrödinger equation for atoms, we established quantitatively that the HHG yield can be expressed as the product of a returning electron wave packet and photorecombination cross sections, and the shape of the returning wave packet is shown to be largely independent of the species. By comparing the HHG spectra generated from different targets under identical laser pulses, accurate structural information, including the phase of the recombination amplitude, can be retrieved. This result opens up the possibility of studying the target structure of complex systems, including their time evolution, …
Signature Of Ericson Fluctuations In Helium Inelastic Scattering Cross Sections Near The Double Ionization Threshold, Junliang Xu, Anh-Thu Le, Toru Morishita, C. D. Lin
Signature Of Ericson Fluctuations In Helium Inelastic Scattering Cross Sections Near The Double Ionization Threshold, Junliang Xu, Anh-Thu Le, Toru Morishita, C. D. Lin
Physics Faculty Research & Creative Works
We calculated the inelastic electron impact excitation cross sections of He⁺ by electrons for a model helium atom to examine the onset of the signature of quantum chaotic scattering in this simple system. We find Ericson fluctuations (EF) in the calculated inelastic scattering cross sections only when the impact energies lie within about 0.21 eV below the double ionization threshold. We also discuss the stringent requirements and the proper methods for analyzing the inelastic scattering cross sections in order to observe EF experimentally.
Photoionization Broadening Of The 1s-2s Transition In A Beam Of Atomic Hydrogen, Nikolai N. Kolachevsky, Martin K. Haas, Ulrich D. Jentschura, Maximilian Herrmann, Peter Fendel, Marc P. Fischer, Ronald Holzwarth, Th H. Udem, Christoph H. Keitel, Theodor Wolfgang Hansch
Photoionization Broadening Of The 1s-2s Transition In A Beam Of Atomic Hydrogen, Nikolai N. Kolachevsky, Martin K. Haas, Ulrich D. Jentschura, Maximilian Herrmann, Peter Fendel, Marc P. Fischer, Ronald Holzwarth, Th H. Udem, Christoph H. Keitel, Theodor Wolfgang Hansch
Physics Faculty Research & Creative Works
We consider the excitation dynamics of the two-photon 1S - 2S transition in a beam of atomic hydrogen by 243 nm laser radiation. Specifically, we study the impact of ionization damping on the transition line shape, caused by the possibility of ionization of the 2S level by the same laser field. Using a Monte Carlo simulation, we calculate the line shape of the 1S - 2S transition for the experimental geometry used in the two latest absolute frequency measurements [M. Niering, Phys. Rev. Lett. 84, 5496 (2000) and M. Fischer, Phys. Rev. Lett. 92, 230802 (2004)]. The calculated line shift …
New Limits On The Drift Of Fundamental Constants From Laboratory Measurements, Marc P. Fischer, Nikolai N. Kolachevsky, Marcus Zimmermann, Ronald Holzwarth, Th H. Udem, Theodor Wolfgang Hansch, Michel Abgrall, Jan Grunert, Ivan Maksimovic, Sebastien Bize, Harold Marion, Franck Pereira M Dos Santos, Pierre Lemonde, Giorgio Santarelli, Ph Laurent, Andre Clairon, Christophe Salomon, Martin K. Haas, Ulrich D. Jentschura, Christoph H. Keitel
New Limits On The Drift Of Fundamental Constants From Laboratory Measurements, Marc P. Fischer, Nikolai N. Kolachevsky, Marcus Zimmermann, Ronald Holzwarth, Th H. Udem, Theodor Wolfgang Hansch, Michel Abgrall, Jan Grunert, Ivan Maksimovic, Sebastien Bize, Harold Marion, Franck Pereira M Dos Santos, Pierre Lemonde, Giorgio Santarelli, Ph Laurent, Andre Clairon, Christophe Salomon, Martin K. Haas, Ulrich D. Jentschura, Christoph H. Keitel
Physics Faculty Research & Creative Works
We have remeasured the absolute 1S-2S transition frequency νH in atomic hydrogen. A comparison with the result of the previous measurement performed in 1999 sets a limit of (-29 ± 57) Hz for the drift of νH with respect to the ground state hyperfine splitting νCs in 133Cs. Combining this result with the recently published optical transition frequency in 199Hg+ against νCs and a microwave 87Rb and 133Cs clock comparison, we deduce separate limits on α˙ / α = (-0.9 &plusm; 2.9) x 10-15 yr-1 and the fractional time …
Self-Energy Correction To The Two-Photon Decay Width In Hydrogenlike Atoms, Ulrich D. Jentschura
Self-Energy Correction To The Two-Photon Decay Width In Hydrogenlike Atoms, Ulrich D. Jentschura
Physics Faculty Research & Creative Works
We investigate the guage invariance of the leading logarithmic radiative correction to the two-photon decay width in hydrogenlike atoms, was investigated. The effective treatment of the correction using a Lamb-shift led to the equivalent results in both the length and velocity gages. The relevant radiative corrections were found to be related to the energies that entered into the propagator denominators, to the Hamiltonian, to the wave functions, and to the energy conservation condition, that holds between two photons. The results show that the dominant radiative correction to the 2S two-photon decay width is about -2.020 536(α/π)(Zα)2 1n[(Zα)-2] …
Lamb Shift Of Laser-Dressed Atomic States, Ulrich D. Jentschura, Jorg Evers, Martin K. Haas, Christoph H. Keitel
Lamb Shift Of Laser-Dressed Atomic States, Ulrich D. Jentschura, Jorg Evers, Martin K. Haas, Christoph H. Keitel
Physics Faculty Research & Creative Works
We discuss radiative corrections to an atomic two-level system subject to an intense driving laser field. It is shown that the Lamb shift of the laser-dressed states, which are the natural state basis of the combined atom-laser system, cannot be explained in terms of the Lamb shift received by the atomic bare states which is usually observed in spectroscopic experiments. In the final part, we propose an experimental scheme to measure these corrections based on the incoherent resonance fluorescence spectrum of the driven atom.
Two-Loop Bethe-Logarithm Correction In Hydrogenlike Atoms, Krzysztof Pachucki, Ulrich D. Jentschura
Two-Loop Bethe-Logarithm Correction In Hydrogenlike Atoms, Krzysztof Pachucki, Ulrich D. Jentschura
Physics Faculty Research & Creative Works
We calculate the two-loop Bethe logarithm correction to atomic energy levels in hydrogenlike systems. The two-loop Bethe logarithm is a low-energy quantum electrodynamic (QED) effect involving multiple summations over virtual excited atomic states. Although much smaller in absolute magnitude than the well-known one-loop Bethe logarithm, the two-loop analog is quite significant when compared to the current experimental accuracy of the 1 S – 2 S transition: It contributes - 8.19 and - 0.84 k H z for the 1 S and the 2 S state, respectively. The two-loop Bethe logarithm has been the largest unknown correction to the hydrogen Lamb …
Non-Sequential Double Ionization Of Ne In Intense Laser Pulses: A Coincidence Experiment, Robert Moshammer, Bernold Feuerstein, Daniel Fischer, Alexander Dorn, Claus Dieter Schroter, J. Deipenwisch, Jose R. Crespo Lopez-Urrutia, C. Hohr, Paul B. Neumayer, Joachim Hermann Ullrich, Horst Rottke, Christoph Trump, M. Wittmann, Georg Korn, Wolfgang Sandner
Non-Sequential Double Ionization Of Ne In Intense Laser Pulses: A Coincidence Experiment, Robert Moshammer, Bernold Feuerstein, Daniel Fischer, Alexander Dorn, Claus Dieter Schroter, J. Deipenwisch, Jose R. Crespo Lopez-Urrutia, C. Hohr, Paul B. Neumayer, Joachim Hermann Ullrich, Horst Rottke, Christoph Trump, M. Wittmann, Georg Korn, Wolfgang Sandner
Physics Faculty Research & Creative Works
The dynamics of Neon double ionization by 25 fs, 1.0 PW/cm2 laser pulses at 795 nm has been studied in a many particle coincidence experiment. The momentum vectors of all ejected atomic fragments (electrons and ions) have been measured using combined electron and recoil-ion momentum spectroscopy. Electron emission spectra for double and single ionization will be discussed. In both processes the mean electron energies differ considerably and high energetic electrons with energies of more than 120 eV have been observed for double ionization. The experimental results are in qualitative agreement with the rescattering model.