The time-dependent Schr\"odinger equation for H2+ in a time-varying electromagnetic field is solved in the fixed-nuclei approximation using a previously developed finite-element/ discrete variable representation in prolate spheroidal coordinates. Amplitudes for single- and two-photon ionization are obtained using the method of exterior complex scaling to effectively propagate the field-free solutions from the end of the radiation pulse to infinite times. Cross sections are presented for one-and two-photon ionization for both parallel and perpendicular polarization of the photon field, as well as photoelectron angular distributions for two-photon ionization.

# Your search: "author:Rescigno, Thomas N."

## filters applied

## Type of Work

Article (31) Book (0) Theses (0) Multimedia (0)

## Peer Review

Peer-reviewed only (27)

## Supplemental Material

Video (0) Audio (0) Images (0) Zip (0) Other files (0)

## Publication Year

## Campus

UC Berkeley (0) UC Davis (1) UC Irvine (0) UCLA (0) UC Merced (0) UC Riverside (0) UC San Diego (0) UCSF (0) UC Santa Barbara (0) UC Santa Cruz (0) UC Office of the President (0) Lawrence Berkeley National Laboratory (31) UC Agriculture & Natural Resources (0)

## Department

## Journal

## Discipline

## Reuse License

BY-NC-ND - Attribution; NonCommercial use; No derivatives (1)

## Scholarly Works (31 results)

A two-color two-photon atomic double ionization experiment using subfemtosecond UV pulses can be designed such that the sequential two-color process dominates and one electron is ejected by each pulse. Nonetheless, ab initio calculations show that, for sufficiently short pulses, a prominent interference pattern in the joint energy distribution of the sequentially ejected electrons can be observed that is due to their indistinguishability and the exchange symmetry of the wave function.

We report the results of ab initio calculations of cross sections and molecular-frame photoelectron angular distributions for C 1s ionization of CO2, and propose a mechanism for the recently observed asymmetry of those angular distributions with respect to the CO^+and O^+ions produced by subsequent Auger decay. The fixed-nuclei, photoionization amplitudes were constructed using variationally obtained electron-molecular ion scattering wave functions. We have also carried out electronic structure calculations which identify a dissociative state of the CO2^++ dication that is likely populated following Auger decay and which leads to O^+ + CO^+ fragment ions. We show that a proper accounting of vibrational motion in the computation of the photoelectron angular distributions, along with reasonable assumptions about the nuclear dissociation dynamics, gives results in good agreement with recent experimental observations. We also demonstrate that destructive interference between different partial waves accounts for sudden changes with photon energy in the observed angular distributions.

Electron-impact excitation and ionization of helium is studied in the S-wave model. The problem is treated in full dimensionality using a time-dependent formulation of the exterior complex scaling method that does not involve the solution of large linear systems of equations. We discuss the steps that must be taken to compute stable ionization amplitudes. We present total excitation, total ionization and single differential cross sections from the ground and n=2 excited states and compare our results with those obtained by others using a frozen-core model.

The potential energy surfaces corresponding to the long-lived fixed-nuclei electron scatering resonances of H$_2$O relevant to the dissociative electron attachment process are examined using a combination of ab initio scattering and bound-state calculations. These surfaces have a rich topology, characterized by three main features: a conical intersection between the $^2A_1$ and $^2B_2$ Feshbach resonance states; charge-transfer behavior in the OH ($^2\Pi$) + H$^-$ asymptote of the $^2B_1$ and $^2A_1$ resonances; and an inherent double-valuedness of the surface for the $^2B_2$ state the C$_2v$ geometry, arising from a branch-point degeneracy with a $^2B_2$ shape resonance. In total, eight individual seams of degeneracy among these resonances are located.

Electronic structure methods are combined with variational fixed-nuclei electron scattering calculations and nuclear dynamics studies to characterize resonant vibrational excitation and electron attachment processes in collisions between low-energy electrons and CF radicals. Several low-lying negative ion states are found which give rise to strong vibrational excitation and which are expected to dominate the low-energy electron scattering cross sections. We have also studied several processes which could lead to production of negative ions (F- and C-), However, in contrast to other recent predictions, we do not find CF in its ground state to be a significant source of negative ion production when interacting with thermal electrons.