Day 1 :
Keynote Forum
Cristian Bahrim
Lamar University, USA
Keynote: Depolarization of atoms induced by collisions
Biography:
Cristian Bahrim has expertise in atomic collisions and interactions, spectroscopy and quantum optics. He has completed his PhD at the age of 30 years from the University of Paris, Orsay. He is a full professor at Lamar University and Assistant Director of the Office of Undergraduate Research. He is now President of the Texas section of the American Association of Physics Teachers.
Abstract:
Depolarization of atoms is an angular momentum relaxation process which includes misalignment, disorientation and destruction of alignment. Th e alignment relaxation processes are for an axially symmetric ensemble of atoms excited evenly on Zeeman states |JM>; while disorientation is for the case of an asymmetric ensemble of atoms. Depolarization processes offer accurate information about the anisotropic interaction between atoms in the collision. Our quantum mechanical model for Neon*-Helium collisions offers theoretical depolarization rates for a wide temperature range. In particular reports, our KDA misaligment rate coefficients for Ne*(2pi [J=1]) atoms induced by collisions with Helium ground state atoms and comparison with experiments done in atomic discharges at temperatures between 10 K and 3000 K is reported. Our full quantum closecoupling many-channel calculations use a model potential for describing the interaction between Ne*(2pi [J=1]) and Helium ground state atoms and include the Coriolis coupling due to the rotation of the internuclear axis. Th e analysis of isotropic collisions in a gaseous mixture at thermal equilibrium indicates that for temperatures above 77 K the anisotropy factor between the collisional channels determines the dependence of the depolarization rates. For temperatures below 77 K, our rates for the Ne*(2p2 [J=1]) and Ne*(2p10 [J=1]) atoms indicate a greater infl uence from the long-range Coulomb potentials. We can conclude that when the depolarization depends weakly on the long-range Coulomb polarization and van der Waals potentials, the cross sections for our intra- and inter-multiplet transitions tend to have a linear variation toward the zero collision energy limit. Our quantum calculations indicate that for the Ne*(2p2) and Ne*(2p10) atoms at low collision energies, below 10 meV, the rotation of the atomic nuclei has a greater infl uence in the Hamiltonian of the Neon* - Helium system than the electrostatic interaction. Th is does not happen for the other atomic states, such as the 2p5 and 2p7 states, where the long-range part of the anisotropy in the electrostatic interaction has a much larger value. Our study helps to better understand the infl uence of collisions to the stability of atomic susceptibilities for quantum systems coupled with two or more lasers which are set up in an electromagnetically induced transparency regime and suggests the importance of inter- and intra-multiplet transitions to the thermal stability of quantum optical memories.
Keynote Forum
Athanasios Petridis
Drake University, USA
Keynote: Time-dependent quantum mechanics in particle and nuclear physics
Biography:
Dr. Athanasios Petridis completed his Ph.D. degree in Theoretical Particle Physics at Iowa State University in 1992. He was a member for the PHENIX collaboration which produced the fi rst evidence for Quark-Gluon Plasma for eight years. He is currently a faculty member and Chairman of the Department of Physics and Astronomy at Drake University in Des Moines, Iowa where he teaches and is engaged in research on theoretical particle and nuclear physics together with his students. He is the author or co-author of many papers in reputed journals. His work has been cited many thousands of times. He is also an academic editor of the Current Journal of Applied Science and Technology.
Abstract:
Time-dependent non-relativistic and relativistic quantum mechanics has been extensively used in atomic physics. It also allows for detailed studies of the development of systems in particle and nuclear physics not only for asymptoticallyfree states but also for states in the non-perturbative regime. It reveals rich phenomena that are not accessible with timeindependent calculations. Some examples are the non-exponential decay of quantum systems including atomic and nuclear, survival probabilities of quarkonia in heavy-ion collisions, relativistic quantum interference and the Aharonov-Bohm eff ect, relativistic dynamic mass renormalization and others. It can also be used to calculate bound states by introducing imaginarytime propagation as well as the time-evolution of coupled fermion systems such as quarks bound in heavy and light mesons.In this talk several examples of non-relativistic and relativistic systems will be presented using analytical calculations when possible and numerical calculations for more complex problems. Th e computational challenges, especially those related to non-linear equations, will be discussed together with some very eff ective solutions. Th e time-dependent methods are very efficient in solving complex problems without the need of obtaining eigenvalues and eigenstates for interacting systems and the use of relatively small computational facilities. Th e relativistic, time-dependent Aharonov-Bohm eff ect. Th e electron probability density propagating diagonally is asymmetrically diff racted around aa very long, impenetrable solenoid that is placed perpendicularly to the plane at the center.
Keynote Forum
Alla S Safronova
University of Nevada-Reno, USA
Keynote: Atomic physics, spectroscopy and fusion applications of tungsten
Time : 11:50-12:35
Biography:
Alla S Safronova received her Ph.D. degree in atomic physics from the Institute of General Physics, Russian Academy of Science (RAS), Moscow in 1986. She joined University of Nevada, Reno (UNR) in 1994, where currently she is a Research Professor. She is one of the pioneers in the application of x-ray line polarization to astrophysical and laboratory plasmas and has published more than 220 papers on atomic and plasma physics. Her former PhD students are working at Sandia National Laboratories, Naval Research Laboratory, UNR and also abroad. She organized, chaired and co-chaired the series of International Workshops on Radiation from High Energy Density Plasmas (RHEDP 2011, 2013 and 2015) and the 10th International Conference on Dense Z-pinches (2017). Prof. Safronova was the Guest Editor of the Fifth Special Issue (2012) and now of the Seventh Special Issue (2018) on Z-Pinch Plasmas of the IEEE Transactions on Plasma Science and of the Special Topic Section on RHEDP of Physics of Plasmas in 2014 and 2016.
Abstract:
Tungsten is a high atomic number, mass and density metal (W, Z=74, 183.84 amu and 19.3 g/cm3 respectively) that was extensively studied and has been found to have a lot of applications in atomic, nuclear and plasma physics, chemistry, biology as well as in industry, since its discovery in 1781. Tungsten is now considered one of the best candidate materials for fusion reactors: it carries heat away effi ciently, has the highest melting point of all metals and has low sputtering yield and tritium retention. In addition, recently a W divertor was implemented in the ITER (International Thermonuclear Experimental Reactor) project. Th e presence of heavy elements in the otherwise low-Z tokamak plasma may cause radiation losses that substantially infl uence the ignition of the plasma. Initially neutral, the W atoms can be collisionally ionized when moving to the hotter plasmas and it might become possible that W plasmas can reach the reactor core where they attain very high temperatures. Hence, tungsten will radiate a very broad spectrum from a few times ionized up to more than sixty times ionized, which is very challenging for the interpretation, modeling and comprehensive analysis. In this talk, we consider dielectronic recombination as a very important atomic process in laboratory and astrophysical plasmas and methods of calculations of W relativistic atomic data. In particular, we present the results of relativistic energy levels, radiative probabilities, autoionization rates and dielectronic satellite spectra of W in a very broad range of ionization stages from fi ve times ionized (Tm-like W5+) to forty fi ve times ionized (Cu-like W45+) to such very high ionization stages as seventy one times ionized (Li-like W71+) tungsten [1-6] (see Figure). A comparison between the results from various relativistic atomic structure codes and accuracy of atomic data is discussed. Another important application of tungsten is in z-pinch physics and ICF (Inertial Confi nement Fusion): wire arrays that consist of hundreds of micron- diameter W wires can be imploded at multi-MA currents and generate the highest radiation yield out of all other wire materials. Not only multi-MA but also 1 MA university-scale pulsed power generators are able to produce multiply-ionized high-Z plasma [7-8], which is illustrated in this talk for W z-pinches. Specifi cally, x-ray spectra from 1 to 10 Å from various W wire loads are presented and analyzed. Future work relevant to both atomic and nuclear physics is discussed. This research was supported by the National Nuclear Security Administration and the Office of Science of the U.S. Department of Energy.
- Workshop
Location: Meeting Room 3
Chair
Igor M Savukov
Los Alamos National Laboratory, USA
Session Introduction
Igor M Savukov
Los Alamos National Laboratory, USA
Title: Applications of many-body perturbation theory to actinide atoms
Biography:
Igor M Savukov has completed his PhD in 2002 at the University of Notre Dame, in the USA and in 2006 his postdoctoral studies at Princeton University. Currently, he is an R&D Scientist at Los Alamos National Laboratory. He has published 80 papers in reputed journals, h index 22 and has been working over 20 years in the field of atomic structure calculations especially in the field of relativistic many-body theory.
Abstract:
There are three main challenges for accurate applications of atomic theory to calculations of energy levels and other properties of Actinide atoms. First, the valence-valence interaction is strong and requires a large confi guration space to account for this interaction. Various methods have implemented small configuration space and cannot account for the interaction with highly excited states and continuum. Second, the valence-core interaction is also strong and second-order MBPT, which is usually implemented in the confi guration-interaction (CI) many-body perturbation theory (MBPT) method, is not adequate. Finally, the relativistic eff ects are signifi cant breaking the LS-coupling scheme and making the transition amplitudes sensitive to these corrections. Th e approach of relativistic CI-MBPT is quite promising. It proved to give quite accurate results in light atoms, where the valence-core interaction can be described well in the second order and relativistic eff ects can be accounted for by employing Dirac-Fock basis and adding dominant Breit interactions. However, ab initio CI-MBPT completely fails in actinides. Still, signifi cant improvement in accuracy can be achieved by introducing adjustable parameters. In particular, seven such parameters can be used to correct the single-valence energy, while additional two parameters can be used to improve the Coulomb screening. With 9-parameter CI-MBPT approach it is possible to reproduce energy levels in as complex an atom as U I. In this talk, I will show examples of CI-MBPT calculations with adjustable parameters for complex atoms. The work is in progress and some future directions will be also discussed.
- Atomic Physics | Atomic Spectroscopy | Atomic Collisions
Location: Meeting Room 3
Chair
Biswanath Rath
North Orissa University, India
Co-Chair
Mattias Eriksson
Blekinge Institute of Technology, Sweden
Session Introduction
Mattias Eriksson
Blekinge Institute of Technology, Sweden
Title: Total statistical weights of atoms and ions
Biography:
Mattias Eriksson has his expertise in atomic physics and astrophysics. He started his research within atomic physics at Lund University where he took his PhD in 2006. There he did research about hyperfi ne structure of atoms, symbiotic stars (topic of PhD) and radiation processes. After his time in Lund he worked as research fellow at Space telescope science institute in Baltimore, USA and as high school teacher in Jönköping, Sweden. Since 2010 he is working at a University College in Karlskrona, Sweden where he is teaching mathematics and physics. His research is currently within statistical weights and partition functions.
Abstract:
The total statistical weight of an atom or ion equals the number of energy levels of the atom or ions when subjected to a magnetic or an electric field (Zeeman or Stark eff ect). In the theoretical limit of zero perturbation the number of bound levels goes to infi nity, as does the total statistical weight. With a known perturbation the statistical weight is fi nite and can be calculated by summating 2J+1 for all levels which are degenerated in zero electric and magnetic fields, the m levels. The structure of the J states depends on the coupling scheme, the Glebsch-Gordon coeffi cients. The number of levels for each J corresponding to a principal quantum number n is independent of the scheme. Here I will present one formula for the total statistical weight between any chosen principal quantum numbers for any Rydberg Sequence. The statistical weight contribution is surprisingly easy: f(Lp,Sp)∙n2, where Lp and Sp are the orbital and spin angular momentum quantum numbers of the parent term to the Rydberg Sequence. Th is helps improve the calculations of atomic and ionic partition functions. Each m-level makes the contribution of unity to the statistical weight and its contribution to the partition function is exp(-E/kT), where E, k and T are the excitation energy of the level, the Boltzmann's constant and the temperature. Only a tiny fraction of the energy levels of atoms and ions are known (observed) for high values of the principal quantum number so the partition function must be calculated numerically. For low values of perturbation, like in stellar plasmas there are sometimes thousands of bound levels having negligible energy diff erences. Th e statistical weights of those levels are calculated with this formula and then multiplied with the exp(-E/kT) factor to get their contribution to the partition function.
Igor M Savukov
Los Alamos National Laboratory, USA
Title: Ab initio precision CI-MBPT calculations for noble-gas atoms
Biography:
Igor M Savukov has completed his PhD in 2002 at the University of Notre Dame, IN USA and in 2006 his postdoctoral studies at Princeton University. Currently, he is an R&D Scientist at Los Alamos National Laboratory. He has published 80 papers in reputed journals, h index 22 and has been working over 20 years in the field of atomic structure calculations especially in the fi eld of relativistic many-body theory.
Abstract:
Noble gas atoms, important for plasma modeling and other applications are quite diffi cult for theoretical calculations because of large correlation and relativistic corrections. In particular, the particle-hole confi guration-interaction manybody theory (CI-MBPT) has diffi culties due to poor convergence of MBPT for the “hole” states. Recently we found that MBPT convergence and the accuracy of CI-MBPT can be improved by treating eight hole upper s- and p- electrons as valence electrons and by restricting the number of configurations in a certain way to make computation time manageable. We analyzed a large number of transition in Ar and other noble-gas atoms and found that Ar and Ne calculations are in good agreement with experiment, while calculations in heavier noble-gas atoms agree less with experiments, which partially can be attributed to the experiments. Because transition probability data are limited, we also analyzed intensities of discharge emissions, which at certain conditions are correlated with experimental transition probabilities and found that such correlation exists with theoretical calculations as well, especially in the cases where detection effi ciency has been carefully taken into account.
Alla S Safronova
University of Nevada-Reno, USA
Title: Atomic physics, spectroscopy and applications of tungsten
Biography:
Alla S Safronova received her Ph.D. degree in atomic physics from the Institute of General Physics, Russian Academy of Science (RAS), Moscow, in 1986. She joined University of Nevada, Reno (UNR) in 1994, where currently she is a Research Professor. She has published more than 220 papers on atomic and plasma physics. Her former PhD students are working at Sandia National Laboratories, Naval Research Laboratory, at UNR and also abroad. She organized, chaired and co-chaired the series of International workshops on Radiation from High Energy Density Plasmas (RHEDP 2011, 2013 and 2015) and the 10th International Conference on Dense Z-pinches (2017).
Abstract:
Tungsten (W, Za=74) is now considered one of the best candidate materials for fusion reactors: it carries away heat efficiently, has the high melting point, low sputtering yield and tritium retention. Th e ability to melt during the transient events and large Z are among critical issues for tungsten application in fusion reactor and should be investigated in detail. Recently, W divertor was implemented in the ITER project and it became possible that W plasmas can reach the reactor core and then attain very high temperatures. Hence, tungsten might radiate a very broad spectrum from a few times ionized up to more than sixty times ionized, which is very challenging for the interpretation and comprehensive analysis. In this talk, we consider dielectronic recombination as a very important atomic process in laboratory and astrophysical plasmas and present the calculations of relativistic energy levels, radiative probabilities and autoionization rates of W in a very broad range of ionization stages from Yb-like W4+ to Cu-like W45+ to such very high ionization stages as Li-like W71+ [1-3]. A comparison between the results from various relativistic atomic structure codes and accuracy of atomic data is discussed. Another important application of tungsten is in Z-pinch physics: wire arrays that consist of hundreds of micron diameter W wires can be imploded at multi-MA currents and generate the highest radiation yield out of all other wire materials. Not only muti-MA but also 1 MA university-scale pulsed power generators are able to produce multiply-ionized high-Za plasma [4-5], which is illustrated in this talk for W Z-pinches. In particular, x-ray spectra from 1 to 10 Å from W wire loads are presented and analyzed. Future work relevant to both atomic and nuclear physics is discussed. Th is research was supported by National Nuclear Security Administration under DoE grants DE-NA0003047 and DE-NA0002945.
Yuki Nojiri
Toho University, Japan
Title: Zeeman and Stark effects of Ba highly-excited states
Time : 16:35-17:05
Biography:
Yuki Nojiri after graduating from department of physics, Toho University, now he was a graduate student at Toho University. He is interested in atomic physics and currently doing high-resolution laser spectroscopy to study Zeeman and Stark effects.
Abstract:
Zeeman and Stark eff ects, the interactions between the atom and magnetic or electric fi elds are very important for understanding the atomic structure. The fundamental spectroscopic data of the g factor and the electric polarizability are directly related to the atomic wave function and therefore, provide sensitive tests of theoretical calculations. As a heavy twoelectron atom, Ba has rather complicated atomic structure together with strong confi guration mixing in highly excited states and shows repeated interest to spectroscopists up to now. For the 5d6p confi guration, the electric polarizabilities of 3DJ and 3PJ have been reported and found to have large diff erent values. However, there are no data determined for 3FJ. Data for 3FJ are indispensable for checking the systematic behavior of the 5d6p confi guration. Recently we have measured Zeeman and Stark eff ects for 3F2. In this paper we report measurements for 3F3 and 3F4. Th e high-resolution atomic-beam laser spectroscopy was performed to measure Zeeman and Stark spectra. A tunable diode laser with an external cavity system together with a highly collimated atomic beam was used in this experiment. Laser-induced fl uorescence was measured and magnetic or electric field was applied to atomic beam. Transitions from the metastable states 6s5d 3DJ populated by an electric discharge were used. Figure 1 shows the measured spectrum at the zero fi eld for the Ba 6s5d 3D3 5d6p 3F4 transition at 705.9 nm; the peaks of 136Ba and 138Ba are marked and other peaks are the hyperfi ne structure of the odd-isotopes 135Ba and 137Ba. Th e insert in Fig. 1 is the measured Zeeman spectrum at the magnetic fi eld 186.1 G which shows splittings by the magnetic fi eld for 136Ba and 138Ba. Zeeman and Stark spectra were measured at various magnetic and electric fi elds and their shift s and splittings were derived. Therefore, the g factor and scalar and tensor polarizabilities were determined for 5d6p 3F3 and 3F4. Together with the previously reported values on 3F2, systematic behaviors of the g factor and scalar and tensor polarizabilities for 3FJ are discussed.
Eric Ouma Jobunga
Technical University of Mombasa, Kenya
Title: Pseudopotential for many-electron atoms
Biography:
Dr. Eric Ouma Jobunga holds a Doctorate degree in Theoretical Physics from Humboldt University of Berlin, a Master’s of Science degree in Atomic Physics and a Bachelor of Education (Science) degree with specialization in Mathematics and Physics from Kenyatta University. He is currently a Physics lecturer and a Chairman of Mathematics and Physics department at the Technical University of Mombasa. His research interests span investigation of the structure of matter and field-matter interaction processes.
Abstract:
Atoms form the basic building blocks of molecules and condensed matter. Other than hydrogen atom, all the others have more than one electron which interact with each other besides interacting with the nucleus. Electron-electron correlation forms the basis of diffi culties encountered in many-body problems. Accurate treatment of the correlation problem is likely to unravel some nice physical properties of matter embedded in this correlation. In an eff ort to tackle this many-body problem, two complementary parameter-free pseudopotentials for n-electron atoms and ions are suggested in this study. Using one of the pseudopotentials, near-exact values of the ground state ionization energies of helium, lithium and beryllium atoms have been calculated. Th e other pseudopotential also proves to be capable of yielding reasonable and reliable quantum physical observables within the non-relativistic quantum mechanics.
Alexander N Zinoviev
Ioffe Institute St Petersburg, Russia
Title: Interatomic potentials, atom energy and screening constants
Biography:
Alexander Zinoviev has his expertise in atomic, plasma and nuclear physics. Ðe completed his PhD at the age of 31 and later, in 1992, got the status of Dr Habil from Ioffe Institute in St. Petersburg. He has been selected as a head of the lab of atomic collision in solids. Ðе is a coordinator of the Atomic Physics Research at Ioffe Institute.
Abstract:
Simple formulae for estimating atom energy (the electron subsystem energy of atom) and screening constant have been proposed. The formula for the screening constant fits well experimental data on interaction potentials. Quantitative description of the experiment for the effect of electronic screening on the nuclear synthesis reaction cross-section for the D+/-D system has been obtained. A conclusion has been made that the diff erences between the measured cross-sections and their theoretically predicted values which take place in more complicated cases of nuclear synthesis reactions are not caused by uncertainties in the knowledge of interatomic potentials. The interatomic potential determines the nuclear stopping power in materials. Experimental data prove that the approach of determining interatomic potentials from quasielastic scattering can be successfully used. Experimental data on the scattering of atomic particles were analyzed and an analytical potential form was proposed as the best fi t of the available experimental data. It is shown that Application of any universal potential is limited to internuclear distances R<7 af (af is the Firsov length).Th e paper discusses pair-specifi c interatomic potentials determined both experimentally and by density-functional theory simulations with the DMol approach to choosing basic wave functions. The interatomic potentials calculated using the DMol approach demonstrate an unexpectedly good agreement with experimental data. Diff erences are mainly observed for heavy atom systems, which suggests that they can be improved by extending the basis set and more accurately considering the relativistic eff ects. Th ese data are recommended for modeling collision cascades in ion-solid collisions.New methods to obtain potential parameters from rainbow scattering features in the atom–metal surface collisions are discussed. Obtained results diff er strongly from the known binary potential models. This difference is explained by the infl uence of interaction of the projectile with metal electrons. Observed patterns of black-body radiation.