Open Access. Powered by Scholars. Published by Universities.^{®}

#
Physical Sciences and Mathematics *Commons*^{™}

Open Access. Powered by Scholars. Published by Universities.^{®}

Articles **1** - **30** of ** 34**

## Full-Text Articles in Physical Sciences and Mathematics

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.

#### 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.

#### 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 ^{6}Liatom 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

#### 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 C_{6} 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

#### 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

#### 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

#### 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/R^{7} Casimir-Polder form to a long-range tail - provided by the Wick-rotated term - proportional to cos[2(E_{m} - E_{n})R/(ħc)]/R^{2}, where E_{m} < E_{n} 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

#### 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

#### 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 2P_{1/2} 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-2P_{3/2} fine-structure splitting only for close approach (R < 100a_{0}, where a_{0} 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

#### 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 C_{6} (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 a_{0} ≪ R ≪ a_{0} / α , where a_{0} = ℏ / α m c is the Bohr radius and α is the fine-structure constant, one finds the symmetry-dependent result ...

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

#### 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/Z^{5} (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/Z^{8}. We investigate noncontact friction effects for the interactions of hydrogen, ground-state helium, and metastable helium atoms with α-quartz (SiO_{2}), 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

#### 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 ...

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

#### 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 (E_{0} = 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

#### 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

#### 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).

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

#### 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 2P_{1/2} and 2P_{3/2} 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 ...

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

#### 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 ...

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

#### 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 α_{G}=Gm_{1}m_{2}/(ℏ*c*), where G is Newton's gravitational constant, c is the speed of light, and m_{1} and m_{2} ≫ m_{1} 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

#### 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 v^{4} 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

#### 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 ...

Effect Of Projectile Coherence On Atomic Fragmentation Processes, Michael Schulz, Kisra N. Egodapitiya, Sachin D. Sharma, Aaron C. Laforge, Robert Moshammer, A. A. Hasan, Don H. Madison

#### Effect Of Projectile Coherence On Atomic Fragmentation Processes, Michael Schulz, Kisra N. Egodapitiya, Sachin D. Sharma, Aaron C. Laforge, Robert Moshammer, A. A. Hasan, Don H. Madison

*Physics Faculty Research & Creative Works*

We demonstrate that the projectile coherence can have a major impact on atomic fragmentation processes. This has been overlooked for decades in formal scattering theory and may explain puzzling discrepancies between theoretical and experimental fully differential cross sections for single ionization.

Comparison Of Experiment And Theory For Electron Impact Ionization Of Isoelectronic Atoms And Molecules, Hari Chaluvadi, Kate L. Nixon, Sadek M. Amami, Andrew James Murray, Don H. Madison

#### Comparison Of Experiment And Theory For Electron Impact Ionization Of Isoelectronic Atoms And Molecules, Hari Chaluvadi, Kate L. Nixon, Sadek M. Amami, Andrew James Murray, Don H. Madison

*Physics Faculty Research & Creative Works*

Experimental and Theoretical Triply Differential Cross sections will be presented for low energy electron impact ionization of Ne, CH_{4}, and NH_{3}. The collision mechanisms responsible for the various structures found in the cross sections will be discussed.

Differential Cross Sections For Single Ionization Of H₂ By 75kev Proton Impact, Ujjal Chowdhury, Michael Schulz, Don H. Madison

#### Differential Cross Sections For Single Ionization Of H₂ By 75kev Proton Impact, Ujjal Chowdhury, Michael Schulz, Don H. Madison

*Physics Faculty Research & Creative Works*

We have calculated Triply differential cross sections (TDCS) and doubly differential cross sections (DDCS) for single ionization of H_{2} by 75 keV proton impact using the molecular 3 body distorted wave Eikonal initial state (M3DW-EIS) approach. Previously published measured DDCS-P (differential in the projectile scattering angle and integrated over the ejected electron angles) found pronounced structures at relatively large angles which were interpreted as an interference resulting from the two-centered potential of the molecule.

Thermal Correction To The Molar Polarizability Of A Boltzmann Gas, Ulrich D. Jentschura, Mariusz Puchalski, Peter J. Mohr

#### Thermal Correction To The Molar Polarizability Of A Boltzmann Gas, Ulrich D. Jentschura, Mariusz Puchalski, Peter J. Mohr

*Physics Faculty Research & Creative Works*

Metrology in atomic physics has been crucial for a number of advanced determinations of fundamental constants. In addition to very precise frequency measurements, the molar polarizability of an atomic gas has recently also been measured very accurately. Part of the motivation for the measurements is due to ongoing efforts to redefine the International System of Units (SI), for which an accurate value of the Boltzmann constant is needed. Here we calculate the dominant shift of the molar polarizability in an atomic gas due to thermal effects. It is given by the relativistic correction to the dipole interaction, which emerges when ...

Manipulating Atomic Fragmentation Processes By Controlling The Projectile Coherence, Kisra N. Egodapitiya, Sachin D. Sharma, Ahmad Hasan, Aaron C. Laforge, Don H. Madison, Robert Moshammer, Michael Schulz

#### Manipulating Atomic Fragmentation Processes By Controlling The Projectile Coherence, Kisra N. Egodapitiya, Sachin D. Sharma, Ahmad Hasan, Aaron C. Laforge, Don H. Madison, Robert Moshammer, Michael Schulz

*Physics Faculty Research & Creative Works*

We have measured the scattering angle dependence of cross sections for ionization in p+H_{2} collisions for a fixed projectile energy loss. Depending on the projectile coherence, interference due to indistinguishable diffraction of the projectile from the two atomic centers was either present or absent in the data. This shows that, due to the fundamentals of quantum mechanics, the preparation of the beam must be included in theoretical calculations. The results have far-reaching implications on formal atomic scattering theory because this critical aspect has been overlooked for several decades.

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

#### 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.

Quantitative Rescattering Theory For Laser-Induced High-Energy Plateau Photoelectron Spectra, Zhangjin Chen, Anh-Thu Le, Toru Morishita, C. D. Lin

#### Quantitative Rescattering Theory For Laser-Induced High-Energy Plateau Photoelectron Spectra, Zhangjin Chen, Anh-Thu Le, Toru Morishita, C. D. Lin

*Physics Faculty Research & Creative Works*

A comprehensive quantitative rescattering (QRS) theory for describing the production of high-energy photoelectrons generated by intense laser pulses is presented. According to the QRS, the momentum distributions of these electrons can be expressed as the product of a returning electron wave packet with the elastic differential cross sections (DCS) between free electrons with the target ion. We show that the returning electron wave packets are determined mostly by the lasers only and can be obtained from the strong field approximation. The validity of the QRS model is carefully examined by checking against accurate results from the solution of the time-dependent ...

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 ...

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 ...

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 ...