Laser-induced Coulomb explosion imaging of C₄H₈O isomers

Coulomb explosion imaging (CEI) is a promising technique that can intuitively connect the experimentally measured fragment ion momenta to the original three-dimensional molecular geometry. [DR1] Recent studies demonstrate that CEI triggered by ultrashort, intense near-infrared or X-ray pulses can offer a direct visualization of individual atoms within a molecule with more than ten atoms [1,2]. In most cases, the molecular (or recoil) frame is defined by the momentum vectors of two atomic ions that are uniquely identified by their mass-to-charge ratio. In this work, we investigate laser-induced CEI of C₄H₈O isomers, where oxygen is the only unique atom. We find that the momentum images of each of these molecules are distinct, allowing the differentiation of the isomers. By leveraging multidimensional information from coincidence measurements to lift the degeneracy of the carbon ions, we show that the momentum images of each molecule still provide a clear correspondence to its original molecular structure in real space. Our findings expand the application of CEI to a broader class of chemically relevant molecules and facilitate the differentiation of various isomer structures that may arise in pump-probe experiments.

[1] R. Boll. et al., Nat. Phys. 18, 423–428 (2022).

[2] H.V.S. Lam et al., Differentiating three-dimensional molecular structures using laser-induced Coulomb explosion imaging (2023, submitted).