Tomography of the molecular quantum state by time-resolved electron diffraction

Anatoli A. Ischenko; Lothar Schaefer; John D. Ewbank

doi:10.1117/12.350538

22 June 1999 Tomography of the molecular quantum state by time-resolved electron diffraction

Anatoli A. Ischenko, Lothar Schaefer, John D. Ewbank

Proceedings Volume 3516, 23rd International Congress on High-Speed Photography and Photonics; (1999) https://doi.org/10.1117/12.350538
Event: Twenty-Third International Congress on High-Speed Photography and Photonics, 1998, Moscow, Russian Federation

Abstract

A procedure is described that can be used to reconstruct the quantum state of a molecular ensemble from time-averaged position probability density functions determined by time- resolved electron diffraction (TRED). The procedure makes use of established techniques for evaluating the density matrix and the phase space joint probability density; i.e., the Wigner function. A novel expression for describing electron diffraction intensities in terms of the Wigner function is presented. An approximate variant of the method, neglecting the off-diagonal elements of the density matrix, was tested by analyzing gas electron diffraction data for N₂ in a Boltzmann distribution, and TRED data obtained from the 193 nm photodissociation of CS₂ to carbon monosulfide, CS, at 20, 40, and 120 ns after irradiation. Although the diagonal density matrix elements do not define completely the quantum state of a system, nonetheless, the approximate Wigner functions derived from them display the expected features of a Gaussian-like function in the case of N₂; and, in the case of CS, they are in agreement with other investigations, indicating collision-less vibrational energy transfer mechanisms for nascent CS during the first 20 ns, and collision-induced electronic S(¹D_J) to vibrational CS(X¹(Sigma) _g⁺) energy transfer.

Citation Download Citation

Anatoli A. Ischenko, Lothar Schaefer, and John D. Ewbank "Tomography of the molecular quantum state by time-resolved electron diffraction", Proc. SPIE 3516, 23rd International Congress on High-Speed Photography and Photonics, (22 June 1999); https://doi.org/10.1117/12.350538

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