1. March 09, 2005 Theoretical Calculations of Ion-Atom & Atom-Diatom Collisions Teck Ghee Lee

2. ORNL/UK March 09, 2005 Applications of atomic & molecular collisions cross sections 1.Basic plasma physics 2.Controlled nuclear fusion energy research 3.Astrophysics & Atmospheric physics 4.Industrial applications of low-temperature plasma such as plasma processing, etching, plasma display panel, etc. 5.Lighting science 6.Radiation science and Biological physics 7.Environmental science and technology 8.Surface science, etc.

3. ORNL/UK March 09, 2005 Ion-atom and atom-diatom collisions processes are important in the modeling of many astrophysical environments Information of our cosmos comes from spectroscopy.  Absorption lines  Emission lines Knowledge of atomic and molecular physics helps to unlock the secrets of the star formation and stellar life cycle. New tool, new observations required new atomic and molecular data. Universe, the final frontier…..

4. ORNL/UK March 09, 2005 Electron capture processes in magnetic fusion Inside ITER -plasma diagnostics -charge state balance Electron capture process in ion-atom collisions is important in the modeling of many technical plasmas The transitions following charge transfer are particularly useful for determining the densities of the fully stripped low-Z ions and for measuring ion temperatures and plasma rotation.

5. ORNL/UK March 09, 2005 Coupled-Channel or Close-Coupling Theory A + BC A + [BC] * AC + B General 3-body collision system Elastic Excited Rearrangement Solve time-independent Schrodinger Eqn: O v R A B C r  Born Oppenheimer Approximation Take H 2 + for example:  Base on electronic-nuclear mass ratio ~ 1/1800 a.u.  Nuclei of the molecule are virtually standing still relative to the electron

6. ORNL/UK March 09, 2005 Types of Mechanism Typical Energy (cm -1 ) Typical Energy (eV) Electronic20k – 80 k~10 Vibrational100 – 4k~0.1 Rotational0.1 – 30~0.001 Some general properties: Can write: Use  to solve the TISE equation with appropriate boundary conditions.

7. ORNL/UK March 09, 2005 We write: And Where Arrive at a system of coupled-channel equation: Coupled-Channel or Close-Coupling Theory

8. ORNL/UK March 09, 2005 Part I: Ion-Atom Collisions at Low Energies BO/MO represents the wave function in -set. Jacobi Coordinate Systems A+A+ B+B+ A + + B A + B + e e e James R. Macdonald Laboratory, Kansas State University Atomic, Molecular & Optical Physics Funded by the US Department of Energy

9. ORNL/UK March 09, 2005 Intermediate energy: v o /v e ~ 1. Straight-line trajectory approximation. Low energy: v o /v e << 1. Quantum mechanical effect becomes IMPORTANT. Non-perturbative quantum mechanical approach is required to treat a two-center and 3-Body dynamics. Energy Regime: Introduction

10. ORNL/UK March 09, 2005 A+A+ B+B+ Charge transferElastic, Excitation Rearrangement and Excitation Processes AB+B+ A+A+ B v Ion-Atom collisions at low energy

11. ORNL/UK March 09, 2005  Objectives A proto-type/textbook system and to test our theory for weak-channels-transitions. Experiment is difficult to perform. Behavior of cross sections in low-energy (eV) region. H + + D(1s) Reactions: H + + D(1s) H(1s) + D + H(2p) + D + H + + D(2p) Elastic Charge Transfer Direct Excitation

12. ORNL/UK March 09, 2005 Previous work: B.M. McLaughlin, JPB96 Theory: Semiclassical H + + H(1s) Lee et al, JPB2003 Excitation H(2p) good agreement with ORNL data except at E < 1 keV/amu Capture H(2p) good agreement with ORNL data down to 0.6 keV/amu.

13. ORNL/UK March 09, 2005 Total charge transfer cross sections Data are in reasonable good agreement. This general agreement in total cross section fails to reveal the significant discrepancies among the reported partial cross section. O 8+ + H(1s)O 7+ (nlm) + H + Lee et al, PRA2004

14. ORNL/UK March 09, 2005 Traditional approach is BO: Theory: Born-Oppenheimer (BO) Method BO treats collisions by fixing positions of heavy nuclei. By expanding system wave function: Scattering wave functions do not satisfy the B.C. Existence of long-range spurious couplings. Cross sections not being Galilean invariant. Solve TISE by expanding system wave function: Ad-hoc electron translation factors (ETF), defined in terms of nuclear velocities, have no quantum equivalents. Arbitrary choice of switching function

15. ORNL/UK March 09, 2005 Hyperspherical coordinate system: accounts for the mass dependence. Solutions to B.O. Problems:  Free from the B.O. problems.  Free from ambiguities.  Hyperspherical coordinate method can be applied to any 3-body systems.

16. ORNL/UK March 09, 2005 Adiabatic hyperspherical potential curves D(1s)+H + H(1s)+D + n=2 E=3.7meV

17. ORNL/UK March 09, 2005 HSCC4 HSCC8 ORNL P3CAOCC TDDFT

18. ORNL/UK March 09, 2005 HSCC8 Dalgano SCA TDDFT ORNL H + +H(1s) Newman et al H + +D(1s) Newman et al H + +H(1s) Charge transfer from D(1s) to H(1s)

19. ORNL/UK March 09, 2005    s) collision

20. ORNL/UK March 09, 2005 Part II: Atom-Diatom Collisions at Low Energies O v R X H H  r

21. ORNL/UK March 09, 2005 The aim of this work is to obtain both accurate and comprehensive molecular collisional rate coefficients, that are needed to understand 1)H 2 spectral line formation 2)rovibrational level populations 3)the effects of H 2 on surrounding gas (e.g., heating and cooling) Since these data are potential sources of error in astrophysical models such as a those developed with the plasma simulation code “Cloudy”. The current uncertainties in collision rates have been known to affect the interpretation of the molecular spectra and our understanding of the conditions in interstellar gas. Energy Levels of H 2

22. ORNL/UK March 09, 2005 Observed data Le Bourlot MNRAS 99 Rescaled collisional data Plot of column density (population) ratio N(H 2 ;v=0,j=3)/ N(H 2 ;v=0,j=1) as functions of total column density N(H 2 ). Scatters represent the results of 100 times changes in the collision rates, an uncertainty representative of current dispersion in collision rates at 100 K. Consequently, over a broad range of column densities uncertainties in collision rates preclude the use of the H 2 absorption spectra as probes of the high-redshift universe.

23. ORNL/UK March 09, 2005 Contour plots of the He-H 2 surface as function of H-H separation r and He-H 2 separation R, at angle  = 90 o. O R He H H  r

24. ORNL/UK March 09, 2005 Quenching rate coefficients of He-H 2 collisions [ v=1,j=0 ] Transition [v=1,j=0] to [v=0,j’]

25. ORNL/UK March 09, 2005  dependent potential couplings

26. ORNL/UK March 09, 2005 Transition [v=2,j=0] to [v=1,j’] 2 characteristics contribute to large [1,0] to [0,8] transition: 1.Small energy gap between [1,0] and [0,8] level. 2.Large potential coupling.

27. ORNL/UK March 09, 2005 Elastic cross sectionsDe-excitation cross sections

28. ORNL/UK March 09, 2005 Summary Coupled-Channel method is a powerful tool for evaluating and generating reliable cross sections for many atomic and molecular collisions systems. Serve as a diagnostic tool for other theoretical methods. Accurate collisional cross sections data are important.  Provide a guide to experimental measurement. Improvement of experimental apparatus and techniques. “Turn-key” theoretical tool to create benchmark collision data needed for applications. Theoretical calculations are economical, provided the computing power is available.

29. ORNL/UK March 09, 2005 Future Plan H + H 2 (v,j)H + H 2 (v’,j’) H 2 (v”,j”) + H 2 (v,j) H 2 (v”,j”) + H 2 (v’,j’) H + HD(v,j)H + HD(v’,j’) He + HD(v,j)He + HD(v’,j’) H 2 (v”,j”) + HD(v,j) H 2 (v”,j”) + HD(v’,j’) Ro-vibrational transitions H + H 2 (v,j)H + H + H H 2 (v”,j”) + H 2 (v,j) H 2 (v”,j”) + H + H H + HD(v,j)H + H + D He + HD(v,j)He + H + D H 2 (v”,j”) + HD(v,j) H 2 (v”,j”) + H + D Collision Induced Dissociation of H 2 and HD molecules H + HD(v,j)D + H 2 (v’,j’) (Rearrangement)

30. ORNL/UK March 09, 2005 Collaborators Gary J. Ferland Phillip C. Stancil N. Balakrishnan Robert C. Forrey A. Dalgarno David R. Schultz Harvard-Smithsonian Center for Astrophysics

31. ORNL/UK March 09, 2005 NASA’s space astrophysics missions  have the goal of meeting bold scientific challenges  represent a very large investment  require large arrays of laboratory astrophysics data to improve interpretation of observations and to enable modeling and simulation

32. ORNL/UK March 09, 2005 Background In brief, the availability of the required laboratory astrophysics data falls significantly short of what is actually needed and sponsorship for this research is also far less than what is required Therefore there is an opportunity and a need for the community to address this shortfall of laboratory astrophysics research  Southeast Laboratory Astrophysics Community (SELAC)

33. ORNL/UK March 09, 2005 The Southeast Laboratory Astrophysics Community  SELAC is a community of researchers seeking to address the laboratory astrophysics needs of NASA space missions & ground- based observatories, and the modeling and simulation efforts required to make significant advances in astrophysics  SELAC is a new organization, but is built on the foundation of longstanding strength in laboratory astrophysics in the Southeast  SELAC has been formed and will develop  in order to provide a forum for communication between and within the laboratory astrophysics and the astrophysics communities  in response to the need to increase awareness of the underpinning nature of laboratory astrophysics in seeking answers to important, present challenges in astrophysics

34. ORNL/UK March 09, 2005 A three-level approach to reach our goals  National level  Need to increase the awareness that laboratory astrophysics underpins the interpretation and modeling of a wide range of astrophysics observations  Need national committees to view laboratory astrophysics as a priority and advocate in its favor  Need to stimulate new funding initiatives at NASA (NSF, DOE)  Need to translate the LAW process findings into concrete actions  Regional/broad level  Leverage the regional strength in laboratory astrophysics by setting up an organization to improve communications and undertake new initiatives - SELAC  Organize SELAC to benefit all its members, sponsoring institutions, the astrophysics community, and the mission agencies  Regional/focused level  Encourage and promote individual or multilateral laboratory astrophysics initiatives

35. ORNL/UK March 09, 2005 UK workshop announcement from first page of the SELAC website www.orau.org/selac