A5023912308- Laser-Matter Interactions and Applications
- Atomic and Molecular Physics
- Spectroscopy and Quantum Chemical Studies
- Mass Spectrometry Techniques and Applications
- Advanced Chemical Physics Studies
- Laser-Plasma Interactions and Diagnostics
- Advanced Fiber Laser Technologies
- Laser Design and Applications
- Laser-induced spectroscopy and plasma
- Advanced X-ray Imaging Techniques
- Quantum optics and atomic interactions
- Particle Accelerators and Free-Electron Lasers
- GaN-based semiconductor devices and materials
- Nonlinear Optical Materials Studies
- Ion-surface interactions and analysis
- Cold Atom Physics and Bose-Einstein Condensates
- Spectroscopy and Laser Applications
- Advanced Materials Characterization Techniques
- Particle accelerators and beam dynamics
- Force Microscopy Techniques and Applications
- Nuclear reactor physics and engineering
- Protein Structure and Dynamics
- Scientific Computing and Data Management
- Scientific Measurement and Uncertainty Evaluation
- Terahertz technology and applications
Joint Institute for Laboratory Astrophysics
2018-2021
University of Colorado Boulder
2018-2021
University of Colorado System
2021
Drake University
2015-2016
Los Alamos National Laboratory
2016
Pennsylvania State University
2016
Niagara University
2016
We investigate two-pathway interferences between nonresonant one-photon and resonant two-photon ionization of atomic hydrogen. In particular, we analyze in detail the photoionization mediated by fundamental frequency second harmonic a femtosecond VUV pulse when is tuned near an intermediate state. Following our recent study [Phys. Rev. A 91, 063418 (2015)] such effects with linearly polarized light, similar situation circularly radiation. As consequence richer structure characterized its...
The electron angular distribution after atomic photoionization by the fundamental frequency and its second harmonic is analyzed for a case when of scans region an intermediate state. left-right asymmetry, due to two-pathway interference between nonresonant one-photon resonant two-photon ionization, sharply change as function photon energy. phenomenon exemplified both solving time-dependent Schr\"odinger equation on numerical space-time grid applying perturbation theory ionization hydrogen...
We have performed single-active-electron numerical calculations of neon- and argonlike atoms interacting with short, intense, circularly polarized laser pulses at wavelengths between 10 nm 1000 nm. Our results reveal a surprisingly large change by factor about 100 in the ionization ratio electrons initial states counter-rotating respect to field over corotating previously unexplored intermediate few-photon regime. The physical mechanism behind this observation is related resonant enhanced...
We theoretically study photoelectron angular distributions and related anisotropy parameters for the competition of one- two-photon ionization He in an ultrashort extreme-ultraviolet laser pulse, using numerical results from time-dependent Schrodinger equation. explore transition between two processes variation pulse duration, peak intensity, central frequency or energy. In obtained fixed interference can be observed even (β 2, β 4) odd 1, 3) parameters, respectively, while onset impact...
We analyze the role of difference between central frequencies spectral distributions vector potential and electric field a short laser pulse. The frequency shift arises when is determined as derivative to ensure that both quantities vanish at beginning end derive an analytical estimate show how it affects various light induced processes, such excitation, ionization, high-harmonic generation. Since observables depend on spectrum field, should be taken into account setting avoid...
We study the excitation to Rydberg states in interaction of hydrogen atom with a short, strong laser pulse. Utilizing solutions time-dependent Schr\"odinger equation we find that parity populated angular momentum agrees selection rules for multiphoton resonant absorption at low intensities, if pulse length is not too short. In contrast, effect cannot be observed ultrashort pulses as well long high intensities. further identify signatures population excited via line emissions from $np$ after...
We theoretically investigate the ionization of neonlike atoms by an intense ultrashort circularly polarized laser pulse as a function wavelength, spanning regime from single-photon to multiphoton and tunneling ionization. In order determine dependence probabilities on magnetic quantum number initial state, we perform ab initio numerical calculations corresponding time-dependent Schr\"odinger equation in single-active-electron approximation. Specific emphasis our analysis is given...
We have performed macroscopic calculations for the thin medium or low gas density regime and a central jet using microscopic numerical solutions of time-dependent Schrödinger equation. In case spatial phase distribution broadband Gaussian pulses with negative Porras factor, our theoretical results show an interference pattern in angular below- near-threshold harmonics, which is not present monochromatic Gouy distribution. The due to off-center contributions that are in-phase those at points...
The displacement effect studied in a recent paper [Ivanov et al., Phys. Rev. A 90, 043401 (2014)] atomic ionization by short XUV pulse is investigated more detail. It shown that achieving significant critically depends on the assumption of plateau envelope function electric field, and ramp-on fine-tuned such way drift velocity generated during phase can increase this further. Seemingly minor variations fields defined slightly different ways cause changes final results, particular regarding...
Theoretical aspects of photoelectron angular distributions are discussed with reference to bichromatic ionization by an FEL beam. Specifically, we consider asymmetry in the distribution due interference between paths from fundamental and second harmonic. The case circularly polarized radiation is analyzed detail vicinity intermediate resonance two-photon paths. Similarities differences phenomena non-dipole effects also discussed.
We study the excitation of hydrogen atom by bichromatic circularly polarized laser pulses using numerical solutions time-dependent Schr\"odinger equation. The results are in agreement with selection rules for multiphoton processes such fields, namely, excited states populated which orbital angular momentum and magnetic quantum numbers either both odd or even, independent relative helicity, peak intensity, pulse duration pulses. For co-rotating show that predominantly proceeds to number same...
Abstract Progress in ultrafast science allows for probing quantum superposition states with ultrashort laser pulses the new regime where several linear and nonlinear ionization pathways compete. Interferences of can be observed photoelectron angular distribution past they have been analyzed atoms molecules a single state via anisotropy asymmetry parameters. Those conventional parameters, however, do not provide comprehensive tools emerging research area bright light sources, such as...
We study the reconstruction of a wave packet and corresponding electron dynamics in an atom via photoelectron angular distributions (PADs) pump-probe scheme as function time delay. The method is applied to superposition ground one or two excited states helium representing field-free charge migrations on attosecond timescale form ring currents around core. It based interference between one- two-photon transitions from into continuum. In predictions first- second-order perturbation theory are...
Photoelectron angular distributions are theoretically described for coherent atomic ionization by short intense pulses of VUV radiation, containing both first and second harmonics, when the energy fundamental is in resonance with an intermediate state. The interference between different pathways results a 'left-right' asymmetry, which exhibits profiles as function photon energy.
Achieving a significant displacement, defined as time integral of the vector potential taken over pulse duration, in strong-field atomic ionization critically depends on envelope function used for electric field. Due to sensitivity theoretical predictions details, an experimental realization effect appears be major challenge.
Nuclear magnetic resonance (NMR) spectroscopy is a powerful method for determining three-dimensional structures of biomolecules, including proteins. The protein structure determination process requires measured NMR values to be assigned specific amino acids in the primary sequence. Unfortunately, current manual techniques assignment data are time-consuming and susceptible error. Many algorithms have been developed automate process, with various strengths weaknesses. algorithm described this...