Joint Experimental and Theoretical Study on Vibrational Excitation Cross Sections for Electron Collisions with Diacetylene

Solving Vibronic Dynamics in Electron Continuum

We present a general two-dimensional model of conical intersection between metastable states that are vibronically coupled not only directly but also indirectly through a virtual electron in the autodetachment continuum. This model is used as a test ground for the design and comparison of iterative solvers for resonance dynamics in low-energy electron-molecule collisions. Two Krylov-subspace methods with various preconditioning schemes are compared. To demonstrate the applicability of the proposed methods on even larger models, we also test the performance of one of the methods on a recent model of vibrational excitation of CO2 by electron impact based on three vibronically coupled discrete states in continuum (Renner-Teller doublet of shape resonances coupled to a sigma virtual state) including four vibrational degrees of freedom. Two-dimensional electron energy-loss spectra resulting from electron-molecule scattering within the models are briefly discussed.

Vibronic Coupling through the Continuum in the e+CO_{2} System

We report two-dimensional electron energy-loss spectra of CO_{2}. The high-resolution experiment reveals a counterintuitive fine structure at energy losses where CO_{2} states form a vibrational pseudocontinuum. Guided by the symmetry of the system, we constructed a four-dimensional nonlocal model for the vibronic dynamics involving two shape resonances (forming a Renner-Teller Π_{u} doublet at the equilibrium geometry) coupled to a virtual Σ_{g}^{+} state. The model elucidates the extremely non-Born-Oppenheimer dynamics of the coupled nuclear motion and explains the origin of the observed structures. It is a prototype of the vibronic coupling of metastable states in continuum.