Atomic autoionization in the photo-dissociation of super-excited deuterated water molecules fragmenting into D+ + O+ + D

W. Iskandar; T. N. Rescigno; A. E. Orel; K. A. Larsen; B. Griffin; D. Call; V. Davis; B. Jochim; T. Severt; J. B. Williams; I. Ben-Itzhak; D. S. Slaughter; Th. Weber

doi:10.1039/D3CP02438E

Atomic autoionization in the photo-dissociation of super-excited deuterated water molecules fragmenting into D⁺ + O⁺ + D

W. Iskandar,

^a T. N. Rescigno,*^a A. E. Orel,^b K. A. Larsen,^ac B. Griffin,^ad D. Call,^d V. Davis,^d B. Jochim,^e T. Severt,^e J. B. Williams,^d I. Ben-Itzhak,

^e D. S. Slaughter

^a and Th. Weber

*^a

Author affiliations

* Corresponding authors

^a Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA-94720, USA
E-mail: TNRescigno@lbl.gov, TWeber@lbl.gov

^b Department of Chemical Engineering, University of California, Davis, CA-95616, USA

^c Graduate Group in Applied Science and Technology, University of California, Berkeley, CA-94720, USA

^d Department of Physics, University of Nevada, Reno, NV-89557, USA

^e J. R. Macdonald Laboratory, Department of Physics, Kansas State University, Manhattan, KS-66506, USA

Abstract

We present the relaxation dynamics of deuterated water molecules via autoionization, initiated by the absorption of a 61 eV photon, producing the very rare D⁺ + O⁺ + D breakup channel. We employ the COLd target recoil ion momentum spectroscopy method to measure the 3D momenta of the ionic fragments and emitted electrons from the dissociating molecule in coincidence. We interpret the results using the potential energy surfaces extracted from multi-reference configuration interaction calculations. The measured particle energy distributions can be related to a super-excited monocationic state located above the double ionization threshold of D₂O. The autoionized electron energy shows a sharp distribution centered around 0.5 eV, which is a signature of the atomic oxygen autoionization occurring in the direct and sequential dissociation processes of D₂O⁺* at a large internuclear distance. In this way, an O⁺ radical fragment and a low-energy electron are created, both of which can trigger secondary reactions in their environment.

Physical Chemistry Chemical Physics

Atomic autoionization in the photo-dissociation of super-excited deuterated water molecules fragmenting into D⁺ + O⁺ + D

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