Photoionization Dynamics of Excited Molecular States
Resonance Enhanced Multiphoton Ionization (REMPI) utilizes tunable dye lasers to ionize an atom or molecule by first preparing an excited state by multiphoton absorption and then ionizing that state before it can decay. This process is highly selective with respect to both the initial and resonant intermediate states of the target, and it can be extremely sensitive. In addition, the products of the REMPI process can be detected as needed by analyzing the resulting electrons, ions, fluorescence, or by additional REMPI. This points to a number of opportunities for exploring excited state physics and chemistry at the quantum-state-specific level. Here we will first give a brief overview of the large variety of experimental approaches to excited state phenomena made possible by REMPI. Then we will examine in more detail, recent studies of the three photon resonant, four photon (3+1) ionization of H2 via the C 1Πu state. Strong non-Franck-Condon behavior in the photoelectron spectra of this nominally simple Rydberg state has led to the examination of a variety of dynamical mechanisms. Of these, the role of doubly excited autoionizing states now seems decisive. Progress on photoelectron studies of autoionizing states in H2, excited in a (2+1) REMPI process via the E,F 1Σ g + will also be briefly discussed.
KeywordsManifold Photodissociation Ectron
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- Achiba, Y. and Kimura, K., 1984, Absorption and ionization of super-excited Rydberg states studied by two-color laser multiphoton ionization technique combined with photoelectron spectroscopy. In Book of Abstracts, International Conference on Multiphoton Processes III, Crete, P13.Google Scholar
- Cornaggia, C., Giusti-Suzor, A., and Jungen, Ch., 1987, Photoionization of the E,F excited state of H2: Calculation of the vibrational and angular distributions of the photoelectrons. To be published.Google Scholar
- Dill, D., 1972, Angular distributions of photoelectrons from H2: Effects of rotational autoionization. Phys. Rev. A6, 160.Google Scholar
- Dill, D., 1976, A primer on photoelectron angular distributions. In Photoionization and Other Probes of Many Electron Interactions, ed. F. Wuilleumier, pp. 387. New York, New York: Plenum.Google Scholar
- Hickman, A. P., 1987a, Photoionization and photodissociation of H2 through autoionizing states. Bull. Am. Phys. Soc. 32, 1252.Google Scholar
- Hickman, A. P., 1987b, Non-Franck-Cgndon distribution of final states in photoionization of H2 (C Hu). Submitted for publication.Google Scholar
- Huber, K. P., and Herzberg, G., 1979, Molecular Spectra and Molecular Structure IV. Constants of Diatomic Molecules. New York, New York: Van Nostrand Reinhold.Google Scholar
- Pratt, S. T., Dehmer, P. M., and Dehmer, J. L., 1987b, Photoionization dynamics of excited molecular states. D2 C ‘Re. Submitted to J. Chem. Phys.Google Scholar
- Xu, E., Tsuboi, T., Kachru, R., and Helm, H., 1987, Four-photon ionization and dissociation of H2. Post-deadline paper, 18th Annual Meeting of the APS Division of Atomic, Molecular, and Optical Physics, Cambridge, MA.Google Scholar