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The role of asymptotic states in H 3 +

The role of asymptotic states in H 3 +. Jonathan Tennyson Department of Physics and Astronomy Royal Society University College London Jan 2006. HPCx supercomputer: Daresbury Laboratory. Spectroscopy of H 3 +.

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The role of asymptotic states in H 3 +

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  1. The role of asymptotic states in H3+ Jonathan Tennyson Department of Physics and Astronomy Royal Society University College London Jan 2006 HPCx supercomputer: Daresbury Laboratory

  2. Spectroscopy of H3+ Meilke et al, Phys. Rev. Lett. 91, 063201 (2003) “Solved problem” at low energy How about near dissociation? • Nature of (rotation-)vibration states? • Radiative association: H2 + H+ H3+ + hn • Isotope exchange eg HD + H3+  H2 + H2D+

  3. Accurate H3+ PES Realistic potential energy surface: Polyansky et al, Mol. Phys., 98, 261 (2000). R q r Jacobi coordinates

  4. Even states Density of states: requires serious computer power

  5. H3+ near dissociation vibrational state

  6. Calculated rotational constants for H3+ JJ Munro, J Ramanlal & J Tennyson, New J Phys, 7, 196 (2005)

  7. Classical trajectory at 19600 cm-1 q=90 R r

  8. Poincare surface of section at 19600 cm-1 p r

  9. Classical trajectoryabove dissociation q=90 R “Feshbach” resonance r

  10. Poincare surface of section for D0 > E > De

  11. CO2 laser: 800 – 1000 cm-1 Detects H+ Creates H3+ H3+ + hn H2 + H+ Near-dissociation photodissociation experiment of Carrington et al

  12. Quantum states at dissociation: Near dissociation spectrum of H3+ by Carrington et al 25000+ discrete lines in 222 cm-1

  13. Technique for characterising resonances • Solve H0F0 = E F0for all E including > D0. • Solve H = H0 + il U(R) for F0 dropping bound solutions; i U(R) is complex absorbing potential (CAP). 3. Vary l to identify resonances in complex plane.

  14. Continuum wavefunction q= 90 R r

  15. Complex Absorbing Potential (CAP) comparison

  16. Locating resonances using a CAP Width Position

  17. Vibrational (Feshbach) resonances Width (G) > 1 cm-1 Too short lived to be important for photodissociation spectrum

  18. Shape resonances: rotational states trapped by centrifugal barrier KE release

  19. Complete model of H3+ near-dissociation photodissocation spectrum • Vibrational states @ dissociation + above • Rotational states @ dissociation + above • Resonances: lifetime effects • Dipole transitions: spectroscopy Asymptotic Vibrational States (AVS) • Robust • Present in other (all?) molecules eg O3, NO2

  20. ChemReact High Performance Computing Consortium Paolo Barletta Bruno Silva James Munro

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