Research ArticleMOLECULAR DYNAMICS

Observation and ultrafast dynamics of a nonvalence correlation-bound state of an anion

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Science Advances  19 May 2017:
Vol. 3, no. 5, e1603106
DOI: 10.1126/sciadv.1603106
  • Fig. 1 Structure of the molecular cluster.

    The equilibrium anion (A) and neutral (B) geometries of the pTQ trimer. The blue dashed lines indicate hydrogen bonds responsible for cohesion of the cluster. (C) The natural orbital associated with the CBS at the neutral geometry.

  • Fig. 2 Photoelectron imaging and dynamics of the CBS of (pTQ)3.

    (A) The photoelectron spectrum taken at hν = 3.10 eV with vibrational structure, together with an exemplary vibrational mode involving ring stretching and puckering that likely contributes to the vibrational structure. (B) Three examples of background-corrected time-resolved photoelectron spectra are shown. The inset shows the t = 150 fs velocity map image from which one of the spectra was derived and shows that the narrow high-eKE peak has an anisotropic angular distribution (β2 ~ +1) that is parallel with the laser polarization vector, ε. (C) The integrated contributions of the low/high eKE features, as a function of pump-probe delay, t, show a fast and slow depletion/recovery that are assigned to internal conversion and autodetachment, respectively. The inset shows the fitted contribution of each relaxation pathway used to extract the lifetimes.

  • Fig. 3 Schematic illustration of the relaxation processes and photoelectron behavior following photoexcitation of (pTQ)3.

    (A) The femtosecond pump pulse excites a π* resonance (t ~ 0) (bold line). The femtosecond probe pulse generates a broad distribution of photoelectrons (PEs) due to the difference between anion and neutral geometries. (B) Resonance population internally converts (τ1 < 60 fs) to the nonvalence CBS (bold line). The photoelectron spectrum associated with the CBS is narrow because the CBS potential energy surface is nearly parallel to that of the neutral. (C) The CBS autodetaches (τ2 = 700 ± 100 fs), mediated by specific vibrational modes of the cluster leading to the structured spectrum at low kinetic energy (Fig. 2A).

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/5/e1603106/DC1

    Electron affinity determination

    Comparison of the dynamics with (CQ0)2

    Details of the π* resonances

    Other cluster geometries

    Multipole moments

    fig. S1. hν = 4.13 eV (300 nm) and hν = 4.43 eV (270 nm) photoelectron spectra of pTQ3.

    fig. S2. CASSCF natural orbitals.

    fig. S3. Geometries, relative energies, dipole moments, and Boltzmann populations of pTQ3 low-lying isomers.

    fig. S4. Dipole moment vector of pTQ3 minimum energy structure along with the natural orbital of the nonvalence state.

  • Supplementary Materials

    This PDF file includes:

    • Electron affinity determination
    • Comparison of the dynamics with (CQ0)2
    • Details of the π* resonances
    • Other cluster geometries
    • Multipole moments
    • fig. S1. hν = 4.13 eV (300 nm) and hν = 4.43 eV (270 nm) photoelectron spectra of pTQ3.
    • fig. S2. CASSCF natural orbitals.
    • fig. S3. Geometries, relative energies, dipole moments, and Boltzmann populations of pTQ3 low-lying isomers.
    • fig. S4. Dipole moment vector of pTQ3 minimum energy structure along with the natural orbital of the nonvalence state.

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