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Peterka DS, Kim JH, Wang CC, et al. Photoionization dynamics in pure helium droplets. J Phys Chem A. 2007;111(31):7449-59doi: 10.1021/jp0710032.
Peterka, D. S., Kim, J. H., Wang, C. C., Poisson, L., & Neumark, D. M. (2007). Photoionization dynamics in pure helium droplets. The journal of physical chemistry. A, 111(31), 7449-59. https://doi.org/10.1021/jp0710032
Peterka, Darcy S, et al. "Photoionization dynamics in pure helium droplets." The journal of physical chemistry. A vol. 111,31 (2007): 7449-59. doi: https://doi.org/10.1021/jp0710032
Peterka DS, Kim JH, Wang CC, Poisson L, Neumark DM. Photoionization dynamics in pure helium droplets. J Phys Chem A. 2007 Aug 09;111(31):7449-59. doi: 10.1021/jp0710032. Epub 2007 Jun 16. PMID: 17571863.
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J Phys Chem A. 2007 Aug 09;111(31):7449-59. doi: 10.1021/jp0710032. Epub 2007 Jun 16.

Photoionization dynamics in pure helium droplets.

The journal of physical chemistry. A

Darcy S Peterka, Jeong Hyun Kim, Chia C Wang, Lionel Poisson, Daniel M Neumark

Affiliations

  1. Department of Chemistry, University of California, Berkeley, California 94720, USA.

PMID: 17571863 DOI: 10.1021/jp0710032

Abstract

The photoionization and photoelectron spectroscopy of pure He droplets were investigated at photon energies between 24.6 eV (the ionization energy of He) and 28.0 eV. Time-of-flight mass spectra and photoelectron images were obtained at a series of molecular beam source temperatures and pressures to assess the effect of droplet size on the photoionization dynamics. At source temperatures below 16 K, where there is significant production of clusters with more than 10(4) atoms, the photoelectron images are dominated by fast electrons produced via direct ionization, with a small contribution from very slow electrons with kinetic energies below 1 meV arising from an indirect mechanism. The fast photoelectrons from the droplets have as much as 0.5 eV more kinetic energy than those from atomic He at the same photon energy. This result is interpreted and simulated within the context of a "dimer model", in which one assumes vertical ionization from two nearest-neighbor He atoms to the attractive region of the He2+ potential energy curve. Possible mechanisms for the slow electrons, which were also seen at energies below IE(He), are discussed, including vibrational autoionizaton of Rydberg states comprising an electron weakly bound to the surface of a large HeN+ core.

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