ezDyson

ezDyson is a C++ code that calculates absolute photodetachment/photoionization cross-sections, photoelectron angular distributions and beta anisotropy parameters using Dyson orbitals computed by an ab initio program. The model used in the calculations is based on the dipole and sudden ionization approximations, and neglects the interaction between the outgoing electron and the ionized core.

Dyson orbitals are defined as the overlap between an N electron molecular wavefunction and the N-1 electron wave function of the ionized system.

They contain all the information about the ionized system required for the cross-section calculation:

where D_k^IF is the photoelectron dipole matrix element connecting the initial and the final wave functions:

The photoelectron is described by a plane wave decomposed in spherical waves basis, |E,l,m>, which contains a radial function, R_kl (spherical Bessel functions for photodetachment and Coulomb functions for photoionization) and the spherical harmonics Y_lm.

The code requires a standard input from quantum chemical calculations (geometries, atomic basis set), details of the experiment (laser polarization, ionization energy, molecular averaging, electron kinetic energies), and the coefficients of the Dyson orbitals in the AO basis and their norms. The ezDyson input is in xml format, and it can be prepared manually. Alternatively, a Python interface can be used to extract data from an electronic structure program. At this point, a Python interface is provided only for the Q-Chem outputs. Dyson orbitals calculations are currently implemented within the EOM-CC suite of methods in Q-Chem. The details of the theoretical model employed as well as benchmark results can be found in the following publications:

[1] C.M. Oana and A.I. Krylov, J. Chem. Phys. 127, 234106 (2007)
[2] C.M. Oana and A.I. Krylov, J. Chem. Phys., in press (2009)

Download ezDyson (including manual.pdf): ezdyson.v1.tar.gz

Download manual: ezDysonManual.pdf

To install, execute:
tar -xzf ezdyson.v1.tar.gz

A general precompiled executable (Linux) is provided, however, the code can be easily recompiled by using an appropriate makefile.

To acknowledge ezDyson use the following citations:
C.M. Oana, V.A. Mozhayskiy and A.I. Krylov, ezDyson, http://iopenshell.usc.edu/downloads

and

"This work was conducted using the resources of the iOpenShell Center for Computational Studies of Electronic Structure and Spectroscopy of Open-Shell and Electronically Excited Species (http://iopenshell.usc.edu) supported by the National Science Foundation through the CRIF:CRF program."