Arbeitsgruppe Prof. Bergmann

4. Outlook - control of the Na3** collision complex

Upon achievement of the desired energy resolution of the ion imaging, it will be implemented to study the mechanisms of the DCT process (2). In fact, the Na2(v") + Na**(nl) collisions leading to the formation of a highly excited  complex is an interesting process to study due to various ionisation channels through which the  complex can decay:







Ionisation channel

Threshold energy [eV]

Na2 (X 1Sg+ ,v??) + Na** (nl)





Na- + Na+ + Na


Na2 + Na++ e-


Na2++ Na + e-


Na2- + Na+


Na2++ Na -




The threshold energies are given in terms of total (electronic, vibrational, and rotational) energy deposited in the Na2 + Na colliding system. Besides the manipulation of the ionisation channels by control of the electronic and vibrational excitation of atoms and molecules, also schemes for coherent laser control are thinkable.



    1. M. Keil, T. Kolling, K. Bergmann, and W. Meyer, "Dissociative attachment of low-energy electrons to vibrationally excited Na2 molecules using a photoelectron source", Eur. Phys. J. D 7, 55 (1999).

    2. J. Bömmels, E. Leber, A. Goplan, J. M. Weber, S. Barsotti, M.-W. Ruf, and H. Hotop, "Energy broadening due to photo-ion space-charge in a high resolution lasre photoelectron source" (in preparation).

    3. F. B. Dunning, "Electron-molecule collisions at very low energies", J. Phys. B 28, 1645 (1995).

    4. O. Kaufmann, A. Ekers, C. Gebauer-Rochholz, K.U. Mettendorf, M. Keil, and K. Bergmann, "Dissociative charge transfer from highly excited Na Rydberg atoms to vibrationally excited Na2 molecules", Int. J. Mass Spectrom. 205, 233 (2001).

    5. M. Matsuzawa, "Rydberg states of atoms and molecules", ed. R. F. Stebbings and F. B. Dunning (Cambridge University Press, New York, 1983) ch. 8.

    6. D. Klar, B. Mirbach, H. J. Korsch, M.-W. Ruf, and H. Hotop, "Comparison of rate coefficients for Rydberg electron and free electron attachment", Z. Phys. D 31, 235 (1994).

    7. A. Ekers, O. Kaufmann, K. Bergmann, J. Alnis, and J. Klavins, "Vibrational effects in Na2(A1u +,v') + Na(3p3/2) associative ionization", Chem. Phys. Lett. 304, 69 (1999).

    8. A. Ekers, O. Kaufmann, M. Keil, and K. Bergmann, "Associative ionization in collisions of electronically excited Na atoms with vibrationally excited Na2(v") molecules", Eur. Phys. J. D 7, 65 (1999).

    9. D. W. Chandler and P. L. Houston, "Two-dimensional imaging of state selected photodissociation products detected by multiphoton ionisation", J. Chem. Phys. 87, 1445 (1987).

    10. A. T. J. B. Eppink and D. H. Parker, "Velocity map imaging of ions and electrons using electrostatic lense: Application in photoelectron and photofragment ion imaging of molecular oxygen", Rev. Sci. Instrum. 68, 3477 (1997).






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