Research ArticleAPPLIED PHYSICS

Deformation of an inner valence molecular orbital in ethanol by an intense laser field

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Science Advances  17 May 2019:
Vol. 5, no. 5, eaaw1885
DOI: 10.1126/sciadv.aaw1885
  • Fig. 1 MO deformation induced by a laser electric field.

    (A) Density functional theory (DFT)–calculated 10a′ (HOMO-1) structures of ethanol in an electric field with strength of 1.7 × 1010 V/m (corresponding to a circularly polarized laser field at an intensity of 8 × 1013 W/cm2) as a function of field direction. The electric field direction is set parallel to the Cs symmetry plane and defined by the angle Φ from the C─C axis of ethanol. Isosurface plots of the MOs 𝚼10a′(Φ) in the electric field with cutoff values of 0.025 (blue) and –0.025 (red) are drawn around that of the field-free MO (Ψ10a′). Inset: Energy level diagram of the field-free MOs in ethanol. The red and black levels have a′ and a″ symmetries, respectively. (B) Overlap populations ∣〈Ψiϒ10a(Φ)〉∣2 of 𝚼10a′(Φ) with the field-free MOs Ψ8a′, Ψ9a′, and Ψ10a′ as functions of angle Φ.

  • Fig. 2 Recoil-frame photoelectron momentum measurements.

    (A) Sketch of relations between the electron tunneling direction (ptunnel), final photoelectron momentum (pele), recoil momentum of the CD2OH+ ion (pCD2OH+), and E-field direction (E) of the circularly polarized (circular pol.) laser field in the experimental setup. TOF, time of flight. (B) Recoil-frame photoelectron momentum distribution for the CD2OH+ channel. The arrow in the image indicates the recoil direction of the fragment ion.

  • Fig. 3 MO deformation effect on the angular-dependent ionization probability.

    (A) DFT-calculated angular-dependent ionization probability of the 10a′ MO [𝚼10a′(Φ, Θ)] in the electric field with E = 1.7 × 1010 V/m. Inset: Defined electric field direction represented with Euler angles (Φ, Θ). (B) Same as (A) but simulated for the field-free 10a′ MO (Ψ10a′). arb. units., arbitrary units. (C and D) Field-deformed MOs 𝚼10a′(Φ, Θ) represented by linear combinations of the field-free MOs Ψ10a′ and Ψ8a′ at (Φ, Θ) = (−112.5°, 90°) and (157.5°, 90°), respectively.

  • Fig. 4 Comparison of theoretical and experimental RFPADs.

    (A) Theoretical RFPADs Ω3a″RFPAD) and Ω10a′RFPAD) from field-deformed 𝚼3a″(Φ, Θ) and 𝚼10a′(Φ, Θ), respectively, in the electric field with E = 1.7 × 1010 V/m. The experimental (exp.) RFPAD is also shown with its vertical error bars. DFT calc., DFT calculations. (B) Same as (A) but simulated for the field-free MOs. (C) Schematic for the tunnel ionization and subsequent processes of CH3CD2OH in the circularly polarized laser field. (D) Comparison of the experimental RFPAD with the linear combination of the theoretical (theo.) RFPADs from the field-deformed MOs (Eq. 1 with f3aexc = 0.48).

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/5/eaaw1885/DC1

    Section S1. Yields of fragment ions produced from CH3CD2OH in the circularly polarized laser field

    Section S2. Comparison of measured RFPAD for the CH3CD2+ production with theoretical RFPADs

    Fig. S1. Electron momentum distributions in the laboratory frame.

    Fig. S2. Ion momentum distributions in the laboratory frame.

    Fig. S3. Out-of-plane angular distributions of electrons with respect to the polarization plane.

    Fig. S4. Scheme of the rotational transformations for derivation of theoretical RFPAD.

    Fig. S5. Time-of-flight mass spectrum of CH3CD2OH.

    Fig. S6. Results for the CH3CD2+ production channel.

    Table S1. The spatial parameters used in the calculations of ethanol.

  • Supplementary Materials

    This PDF file includes:

    • Section S1. Yields of fragment ions produced from CH3CD2OH in the circularly polarized laser field
    • Section S2. Comparison of measured RFPAD for the CH3CD2+ production with theoretical RFPADs
    • Fig. S1. Electron momentum distributions in the laboratory frame.
    • Fig. S2. Ion momentum distributions in the laboratory frame.
    • Fig. S3. Out-of-plane angular distributions of electrons with respect to the polarization plane.
    • Fig. S4. Scheme of the rotational transformations for derivation of theoretical RFPAD.
    • Fig. S5. Time-of-flight mass spectrum of CH3CD2OH.
    • Fig. S6. Results for the CH3CD2+ production channel.
    • Table S1. The spatial parameters used in the calculations of ethanol.

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