Ian Gatland

Professor Emeritus

Research

The long-standing disciplines of theoretical and experimental physics have been joined over the last three decades by that of computational physics. There are many instances in which the basic physics is known (or postulated), and the behavior of a complex system is to be determined. A typical example is that in which there are too many particles for the problem to be tractable in terms of single-particle equations, and too few for a statistical analysis to apply. In such situations, use of a computer may furnish information on enough specific cases for the general behavior of the system to be discernable. If the basis physics is postulated but not known, a computer simulation can relate the theory to observations on complex systems and thus test the theory.

A wide range of numerical techniques are available, from simple searches to sophisticated methods, such as annealing, an algorithm for finding global minima which was inspired by an actual physical process. Some of the techniques are repetitive applications of deterministic equations. Others invoke stochastic processes (using "random" numbers), to focus on the important features.

While most applications of such simulations yield expected results, surprises do occur. This is analogous to an unexpected result from an experiment. Either the simulation/experiment went wrong (usual) or a new aspect of nature has been uncovered (rare). Examples of the latter are the identification of constants of motion in chaotic systems and the discovery of runaway motion in the drift and diffusion of ions in gas. Such discoveries are followed by "proper" theories and "proper" experiments, but the computer plays a vital role in the research.

The research of Professor Gatland involves data analysis and the mathematical modeling and simulation of microscopic physical processes. These activities encompass both research and instruction.

Other Publications

1. "The Effects of a Scalar Meson Interaction Between Muons and Baryons," Nuclear Phys. 9, 267 (1958).
2. "Schwinger's Meson and the :-Mesic Atom," Nuclear Phys. 14, 205 (1959).
3. "Theory of K+ Nucleon Scattering," Nuclear Phys. 15, 480 (1960).
4. "Pion-Pion Scattering Including Inelastic Intermediate States," with B. H. Bransden and J. W. Moffat, Phys. Rev. 128, 859 (1962).
5. "Analytic Approximation to the Low Energy Solutions of Inverse Amplitude Dispersion Relations," with J. W. Moffat, Phys. Rev. 129, 937 (1963).
6. "Singularities in the Angular Momentum Plane," with J. W. Moffat, Phys. Rev. 129, 2812 (1963).
7. "Diffraction Scattering and Singularities in the Angular Momentum Plane," with J. W. Moffat, Phys. Rev. 132, 442 (1963).
8. "Pion-Proton Diffraction Scattering at Very Small Momentum Transfers," with J. W. Moffat, Phys. Rev. 132, 1225 (1963).
9. "Complex Angular Momentum and Diffraction Scattering," with J. W. Moffat, Phys. Letts. 8, 359 (1964).
10. "Boundary Conditions at Infinity for a Single Blocking Electrode," with L. Gold and J. W. Moffat, J. Chem. Phys. 41, 1505 (1964).
11. "Series Solutions of Poisson Equations and Space Charge Theory," with L. Gold, J. Elec. and Control 18, 219 (1965).
12. "Laser Beam Detection of Electron?Photon Interaction," with L. Gold and J. W. Moffat, Phys. Letts. 12, 105 (1964).
13. "Line-Profile Effects in Stimulated Scattering," Phys. Rev. 143, 1156 (1966).
14. "Measurement of Transport Properties of Ions in Gases; Results for K+ Ions in N2," with J. T. Moseley, D. W. Martin, and E. W. McDaniel, Phys. Rev. 178, 234 (1969).
15. "Reply to Longitudinal Diffusion Coefficients Misnamed," by R. N. Varney, with E. W. McDaniel, Phys. Rev. Letts. 25, 1603 (1970).
16. "Ion-Molecule Reactions Between O- and O2 at Thermal Energies and Above," with R. M. Snuggs, D. J. Volz, J. H. Schummers, D. W. Martin, and E. W. McDaniel, Phys. Rev. A3, 487 (1971).
17. "Apparent Pressure Dependence of the Reduced Mobility of Potassium Ions in Gases," Phys. Rev. Letts. 29, 9 (1972).
18. "Mobilities and Longitudinal Diffusion Coefficients of Mass-Identified Positive Ions in Carbon Monoxide Gas," with J. H. Schummers, G. M. Thomson, D. R. James, and E. W. McDaniel, Phys. Rev. A7, 683 (1973).
19. "Measurement of the Rate Coefficient of the Reaction CO+ + 2CO T CO+ " CO + CO in a Drift Tube Mass Spectrometer," with J. S. Schummers, G. M. Thomson, D. R. James, E. Graham and E. W. McDaniel, Phys. Rev. A7, 689 (1973).
20. "Mobility Diffusion and Clustering of K+ Ions in Gases," with G. M. Thomson, J. H. Schummers, D. R. James, E. Graham, M. R. Flannery and E. W. McDaniel, J. Chem. Phys. 58, 2402 (1973).
21. "Mobilities and Longitudinal Diffusion Coefficients of K+ Ions in Argon Gas," with D. R. James, E. Graham IV, G. M. Thomson, and E. W. McDaniel, J. Chem. Phys. 58, 3652 (1973).
22. "Measurement of the Rate Coefficient of the Reactions H+ + 2H2 T H3+ + H2 and D+ + 2D2 T D3+ + D2 in a Drift Tube Mass Spectrometer," with E. Graham IV, D. R. James, W. C. Keever, and E. W. McDaniel, J. Chem. Phys. 59, 4648 (1973).
23. "Analysis for Ion Drift Tube Experiments," Case Studies in Atomic Physics 4, 369 (1974).
24. "Longitudinal Diffusion of K+ Ions in He, Ne, Ar, H2, NO, O2, CO2, N2 and CO," with D. R. James, E. Graham, G. R. Akridge, and E. W. McDaniel, J. Chem. Phys. 62, 1702 (1975).
25. "Single and Double Clustering of Nitrogen to Li+," with L. M. Colonna-Romano and G. E. Keller, Phys. Rev. A 12, 1885 (1975).
26. "Ion Identity and Transport Properties in CO2 Over a Wide Pressure Range," with H. W. Ellis, R. Y. Pai, and E. W. McDaniel, J. Chem. Phys. 64, 3935 (1976).
27. "Tests of Alkali Ion-Inert Gas Interaction Potentials by Gaseous Ion Mobility Experiments," with L. A. Viehland and E. A. Mason, J. Chem. Phys. 66, 537 (1977).
28. "The Li+ - He Interaction Potential," with W. F. Morrison, H. W. Ellis, M. G. Thackston, E. W. McDaniel, M. H. Alexander, L. A. Viehland, and E. A. Mason, J. Chem. Phys. 66, 5121 (1977).
29. "Experimental Test of the Generalized Einstein Relation for Cs+ Ions in Molecular Gases: H2, N2, O2, CO and CO2," with F. L. Eisele, M. G. Thackston, W. M. Pope, H. W. Ellis, and E. W. McDaniel, J. Chem. Phys. 67, 1278 (1977).
30. "Mobilities and Interaction Potentials for Cs+ - Ar, Cs+ - Kr, and Cs+ - Xe," with M. G. Thackston, W. M. Pope, F. L. Eisele, and E. W. McDaniel, J. Chem. Phys. 68, 2775 (1978).
31. "Mobilities and Interaction Potentials for Rb+ - Ar, Rb+ - Kr, and Rb+ - Xe," with D. R. Lamm, M. G. Thackston, W. M. Pope, F. L. Eisele, H. W. Ellis, and E. W. McDaniel, J. Chem. Phys. 69, 4951 (1978).
32. "Mobility and Diffusion of Protons and Deuterons in Helium -- a Runaway Effect," with S. L. Lin and E. A. Mason, J. Phys. B 12, 4179 (1979).
33. "Mobility of Cl- Ions in Ne, Ar, and Kr," with M. G. Thackston, F. L. Eisele, W. M. Pope, H. W. Ellis, and E. W. McDaniel, J. Chem. Phys. 70, 3996 (1979).
34. "Mobilities and Longitudinal Diffusion Coefficients for Na+ Ions in Kr and Xe," with M. G. Thackston, M. S. Sanchez, G. W. Neeley, W. M. Pope, F. L. Eisele, and E. W. McDaniel, J. Chem. Phys. 73, 2012 (1980).
35. "Mobility of Cl- Ions in Xe Gas and the Cl- - Xe Interaction Potential," with M. G. Thackston, F. L. Eisele, W. M. Pope, H. W. Ellis, and E. W. McDaniel, J. Chem. Phys. 73, 3183 (1980).
36. "Mobilities and Interaction Potentials for K+ - Ar, K+- Kr, and K+- Xe," with D. R. Lamm, M. G. Thackston, F. L. Eisele, H. W. Ellis, J. R. Twist, W. M. Pope, and E. W. McDaniel, J. Chem. Phys. 74, 3042 (1981).
37. "Ion Mobility Test of Li+ - Ar Potentials", J. Chem. Phys. 75, 4162 (1981).
38. "The Determination of Potentials for Ion-Atom Interactions by Ion Mobility Experiments," in Electron and Ion Swarms," edited by L. G. Christophorou, Pergamon Press (1981).
39. "Mobilities and Interaction Potentials for Br- - Ar, Br- - Kr, and Br- - Xe," with D. R. Lamm, R. D. Chief, J. R. Twist, F. B. Holleman, M. G. Thackston, F. L. Eisele, W. M. Pope, and E. W. McDaniel, J. Chem. Phys. 79, 1965 (1983).
40. "Determination of Ion Atom Potentials from Mobility Experiments," in "Swarms of Ions and Electrons in Gases," edited by W. Lindinger, T. D. Mark, and F. Howorka, Springer-Verlag (1984).
41. "A 'Vector Calculator' Training Tool," in "Supercomputers," ed. by F. A. Matson and T. Tajima, Univ. of Texas Press, Austin, 1986.
42. "Fast, Accurate Algorithm for Numerical Simulation of Exponentially Correlated Colored Noise," with R. F. Fox, Rajarshi Roy, and Gautam Vemuri, Phys. Rev. A 38, 5938 (1988).
43. "Theory of a Nonharmonic Oscillator," Am. J. Phys. 59, 155-8 (1991).
44. "The Daedalon Ultrasonic Measurement System", Computers in Physics 5, 541-9 (1991).
45. "Experiments Utilizing an Ultrasonic Range Finder", with R. Kahlscheuer and H. Menkara, Am. J. Phys. 60, 451-4 (1992).
46. "Parameter Bias Elimination for Log-Transformed Data with Arbitrary Error Characteristics", with W. J. Thompson, Am. J. Phys. 61, 269-272 (1993).
47. "A Weight-Watchers Guide to Least-Squares Fitting", Computers in Physics 7, 280-285 (1993).
48. "Numerical Integration of Newton's Equations Including Velocity Dependent Forces", Am. J. Phys. 62, 259-265 (1994).
49. "Scalar", Macmillan Encyclopedia of Physics, J. Rigden, Editor, Macmillan Inc., 1996.
50. "Vector", Macmillan Encyclopedia of Physics, J. Rigden, Editor, Macmillan Inc., 1996.
51. "Tensor", Macmillan Encyclopedia of Physics, J. Rigden, Editor, Macmillan Inc., 1996.
52. "Thin Lens Ray Tracing", Am. J. Phys. 70, 1184-1186 (2002).
53. "Nonholonomic Constraints: A Test Case", Am. J. Phys. 72, 941-942 (2004).
54. "Integer Versus Half-Integer Angular Momentum", Am. J. Phys, 74, 191-192 (2006).

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