Molecular structure retrieval directly from laboratory-frame photoelectron spectra in laser-induced electron diffraction

Abstract

Ubiquitous to most molecular scattering methods is the challenge to retrieve bond distance and angle from the scattering signals since this requires convergence of pattern matching algorithms or fitting methods. This problem is typically exacerbated when imaging larger molecules or for dynamic systems with little a priori knowledge. Here, we employ laser-induced electron diffraction (LIED) which is a powerful means to determine the precise atomic configuration of an isolated gas-phase molecule with picometre spatial and attosecond temporal precision. We introduce a simple molecular retrieval method, which is based only on the identification of critical points in the oscillating molecular interference scattering signal that is extracted directly from the laboratory-frame photoelectron spectrum. The method is compared with a Fourier-based retrieval method, and we show that both methods correctly retrieve the asymmetrically stretched and bent field-dressed configuration of the asymmetric top molecule carbonyl sulfide (OCS), which is confirmed by our quantum-classical calculations.

Quantum interference and imaging using intense laser fields

“…LIED's extension to the more advantageous midinfrared (MIR, i.e., λ 2 μm) wavelength range has enabled the direct retrieval of many diatomic and more complex molecular structures [11,23,[79][80][81][82][83][84][85][86][87][88][89]. In fact, not only is the de Broglie wavelength λ B of the rescattering electron significantly smaller for a driving laser at λ = 3 μm (λ B ∼ 0.75 Å) than at λ = 0.8 μm (λ B ∼ 2.75 Å).…”

“…This was only possible with LIED's sub-optical cycle probe of molecular structure together with its sensitivity to hydrogen scattering. Moreover, ultrafast changes on the rising edge of the LIED pulse have been shown to lead to significant structural deformation in C 60 [85], CS 2 [82] and OCS [88].…”

Quantum interference and imaging using intense laser fields

“…LIED's extension to the more advantageous mid-infrared (MIR; i.e. λ 2 µm) wavelength range has enabled the direct retrieval of many diatomic and more complex molecular structures [155,118,119,156,8,6,143,48,94,5,17,125,93]. In fact, not only is the deBroglie wavelength λ B of the rescattering electron significantly smaller for a driving laser at λ = 3 µm (λ B ∼ 0.75 Å) than at λ = 0.8 µm (λ B ∼ 2.75 Å).…”

“…This was only possible with LIED's sub-optical-cycle probe of molecular structure together with its sensitivity to hydrogen scattering. Moreover, ultrafast changes on the rising edge of the LIED pulse have been shown to lead to significant structural deformation in C 60 [48], CS 2 [8] and OCS [125].…”

Resolving Vibrations in a Polyatomic Molecule with Femtometer Precision

“…On the other hand, diffraction methods are commonly used to determine the distances and dynamics within matter using, e.g., electrons [21][22][23][24][25][26][27][28], neutrons [29] or photons [30,31]. For gas-phase molecules, these diffraction methods provide nano-to picometer spatial resolutions.…”