Multiphoton dissociation and ionization of nickelocene

Samuel Leutwyler*, Uzi Even, Joshua Jortner

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

33 Scopus citations

Abstract

In this paper we report the results of an experimental study of collision-free molecular multiphoton dissociation (MPD) and molecular multiphoton ionization (MPI) of nickelocene (NiC10H10), induced by the light of a tunable dye laser in the wavelength region 3750-5200 A. The spectral dependence of the ion signal reveals a multitude of narrow (fwhm from <0.5 cm-1 to 1.5 cm-1) intense peaks superimposed on a very weak background (relative amplitude ratio for peaks/background ≈ 103). The sharp resonances in the ion signal are attributed, on the basis of spectroscopic analysis, to two-photon resonant three-photon ionization of Ni(I) and to one-photon resonant three-photon ionization of Ni(I), the Ni(I) being produced by MPD of nickelocene. The ion signal in the spectral range 3750-3950 A reveals enhanced continuous background due to MPI of nickelocene. This ion signal spectra, together with studies of the intensity dependence of the overall (nickelocene MPD) - (Ni(I) MPI) processes, as well as the (nickelocene molecular MPI) reaction, reveal four reactive processes. (a) Two-photon molecular MPI for hω ≥ 3.10 eV photons. (b) Three-photon molecular MPI for hω = 3.10-2.10 eV. (c) Two-photon MPD at hω ≥ 2.86 eV. (d) Three-photon MPD for hω = 2.8-1.9 eV. The overall dissociation energy of nickelocene (Nicp2) to give Ni + 2cp was determined to be 5.76 ± 0.60 eV and the two-photon ionization potential of this molecule is 6.29 ± 0.015 eV. Our results provide dynamic evidence concerning a simultaneous "explosive" photodissociation mechanism of Nicp2 by process (c) and for the dominating role of the dissociative channel, characterized by a branching ratio of ≥50 in favor of predissociation over autoionization, for process (c) at 6.3-6.6 eV. The MPD processes (c) and (d) are expected to exhibit intramolecular erosion of phase coherence effects. Processes (c) and (d) are of high efficiency ≈0.01 ions/molecule at saturation exhibited at laser power of ≈ 108 W cm-2.

Original languageEnglish
Pages (from-to)409-421
Number of pages13
JournalChemical Physics
Volume58
Issue number3
DOIs
StatePublished - 1 Jan 1981

Funding

FundersFunder number
Stiftung ftir Stipendien auf dem Gebiet der Chemie

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