Resonance enhanced multiphoton and single-photon ionization of molecules and molecular fragments. Final report, May 1993--April 1997
Resonance enhanced multiphoton ionization (REMPI) utilizes pulsed laser radiation to prepare a molecule in an excited state via absorption of one or more photons and to subsequently ionize that level before it decays. A remarkable feature of REMPI is that the very narrow bandwidth of laser radiation makes it possible to select a specific rotational level in the initial (ground) state and to prepare the excited state of interest in a single rotational level. Thus, by suitable choice of the excitation step, it is possible to selectively ionize a species that may be present. The key objective of the effort is to carry out quantitative studies of REMPI of molecules and molecular fragments, as well as of single-photon ionization of these species by coherent VUV radiation, in order to provide a robust description of significant spectral features of interest in related experiments and needed insight into the underlying dynamics of these spectra. A major focus of the effort is joint theoretical and experimental studies of these ion rotational distributions which are being widely studied by the zero-kinetic-energy (ZEKE) technique. This technique, which is based on the detection of photoelectrons resulting from pulsed-field ionization of very high Rydberg states lying just below an ion threshold, makes it possible to obtain cation distributions with subwavenumber resolution. The unprecedented resolution of this ZEKE technique is opening up entirely new vistas in studies of photoionization dynamics, ion spectroscopy, and state-selected ion-molecule reactions. Emerging applications built on the ultra-high resolution of this technique include its use for accurate determination of thermochemically important ionization energies, for characterization of ion rovibrational level structure of large organic molecules, of elemental clusters, and of weakly bound molecular complexes, for probing reactive fragments, and for pump-probe photoelectron studies of wavepacket dynamics. This surge of experimental activity in ultra-high resolution studies of molecular photoelectron spectra continues to raise new theoretical challenges and has provided the stimulus for several of the collaborations with experimental groups in North America and Europe.
- Research Organization:
- California Inst. of Tech., Noyes Lab. of Chemical Physics, Pasadena, CA (United States)
- Sponsoring Organization:
- USDOE Office of Energy Research, Washington, DC (United States)
- DOE Contract Number:
- FG03-87ER60513
- OSTI ID:
- 656804
- Report Number(s):
- DOE/ER/60513-T7; ON: DE98006433; TRN: 99:000487
- Resource Relation:
- Other Information: PBD: [1998]
- Country of Publication:
- United States
- Language:
- English
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