Recent Publications

Daniel Dundas

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  1. Title: Dynamic tunnelling ionization of H-+(2) in intense fields

    Author(s): Peng L.Y., Dundas D., McCann J.F., Taylor K.T., Williams I.D.

    Journal Of Physics B-Atomic Molecular And Optical Physics, 36, No. 18, pp. L295-L302 (SEP 28 2003)

    doi: 10.1088/0953-4075/36/18/101
    Abstract



    Intense-field ionization of the hydrogen molecular ion by linearly polarized light is modelled by direct solution of the fixed-nuclei time-dependent Schrodinger equation and compared with recent experiments. Parallel transitions are calculated using algorithms which exploit massively parallel computers. We identify and calculate dynamic tunnelling ionization resonances that depend on laser wavelength and intensity, and molecular bond length. Results for lambda similar to 1064 nm are consistent with static tunnelling ionization. At shorter wavelengths lambda similar to 790 nm large dynamic corrections are observed. The results agree very well with recent experimental measurements of the ion spectra. Our results reproduce the single peak resonance and provide accurate ionization rate estimates at high intensities. At lower intensities our results confirm a double peak in the ionization rate as the bond length varies.

  2. Title: Dissociative ionization of molecules in intense laser fields

    Author(s): Dundas D., Meharg K.J., McCann J.F., Taylor K.T.

    European Physical Journal D, 26, No. 1, pp. 51-57 (OCT 2003)

    doi: 10.1140/epjd/e2003-00082-0
    Abstract



    Accurate and efficient grid based techniques for the solution of the time-dependent Schrodinger equation for few-electron diatomic molecules irradiated by intense, ultrashort laser pulses are described. These are based on hybrid finite-difference, Lagrange mesh techniques. The methods are applied in three scenarios, namely H-2(+) with fixed internuclear separation, H-2(+) with vibrating nuclei and H-2 with fixed internuclear separation and illustrative results presented.

  3. Title: Laser-driven helium at 780 nm

    Author(s): Taylor K.T., Parker J.S., Meharg K.J., Dundas D.

    European Physical Journal D, 26, No. 1, pp. 67-71 (OCT 2003)

    doi: 10.1140/epjd/e2003-00074-0
    Abstract



    We briefly review the methods under development at Queen's University Belfast to solve the full-dimensionality time-dependent Schrodinger equation for helium in intense laser fields. We set out the computational challenges involved in performing calculations that handle Ti:sapphire laser light at its fundamental wavelength (similar to780 nm) in comparison to those encountered for 390 nm light. We remark upon the very considerable importance of accurate and reliable calculations at 780 nm and present results for single-ionization of helium at this wavelength.

  4. Title: Laser-driven helium, H-2(+) and H-2

    Author(s): Taylor K.T., Parker J.S., Dundas D., Meharg K.J., Moore L.R., McCann J.F.

    Journal Of Modern Optics, 50, No. 3-4, pp. 401-422 (JAN 2003)

    doi: 10.1080/09500340210150460
    Abstract



    We review work carried out in recent years at Belfast devoted to handling the dynamics of laser-driven few-electron atomic and molecular systems in full dimensionality with the goal of bringing quantitative discipline to the field. The design and application of quantitatively accurate computational methods are discussed. Electron-electron correlations induced by intense external fields are observed by calculating the position and momentum space distributions of the doubly ionizing two-electron wave packets and the application of the techniques of scientific visualization analysis to such studies is emphasized. Agreement of results obtained with those from recent laboratory experiments is demonstrated. Work in hand and plans for future calculations are outlined.