title: Quantum Monte Carlo for the x-ray absorption spectrum of pyrrole at the nitrogen K-edge.
abstract: Fixed-node diffusion Monte Carlo (FNDMC) is used to simulate the x-ray absorption spectrum of a gas-phase pyrrole molecule at the nitrogen K-edge. Trial wave functions for core-excited states are constructed from ground-state Kohn-Sham determinants substituted with singly occupied natural orbitals from configuration interaction with single excitations calculations of the five lowest valence-excited triplet states. The FNDMC ionization potential (IP) is found to lie within 0.3 eV of the experimental value of 406.1 ± 0.1 eV. The transition energies to anti-bonding virtual orbitals match the experimental spectrum after alignment of IP values and agree with the existing assignments.
authors.affiliation: Kenneth S. Pitzer Center for Theoretical Chemistry, Department of Chemistry, University of California Berkeley, Berkeley, California 94720-1460, USA.
authors.forename: Dmitry Yu
authors.initials: DY
authors.lastname: Zubarev
authors.forename: Brian M
authors.initials: BM
authors.lastname: Austin
authors.forename: William A
authors.initials: WA
authors.lastname: Lester