A time-dependent Hartree-Fock approach for studying the electronic optical response of molecules in intense fields.
For molecules in high intensity oscillating electric fields, the time-dependent Hartree-Fock (TDHF) method is used to simulate the behavior of the electronic density prior to ionization. Since a perturbative approach is no longer valid at these intensities, the full TDHF equations are used to propagate the electronic density. A unitary transform approach is combined with the modified midpoint method to provide a stable and efficient algorithm to integrate these equations. The behavior of H2+ in an intense oscillating field computed using the TDHF method with a STO-3G basis set reproduces the analytic solution for the two-state coherent excitation model. For H2 with a 6-311++G(d,p) basis set, the TDHF results are nearly indistinguishable from calculations using the full time-dependent Schrödinger equation. In an oscillating field of 3.17 x 10(13) W cm(-2) and 456 nm, the molecular orbital energies, electron populations, and atomic charges of H2 follow the field adiabatically. As the field intensity is increased, the response becomes more complicated as a result of contributions from excited states. Simulations of N2 show even greater complexity, yet the average charge still follows the field adiabatically.
Li
Xiaosong
X
Department of Chemistry, Wayne State University, Detroit, MI 48202, USA.
Smith
Stanley M
SM
Markevitch
Alexei N
AN
Romanov
Dmitri A
DA
Levis
Robert J
RJ
Schlegel
H Bernhard
HB
D003198:Computer Simulation; D004563:Electrochemistry / Q000379:methods; D004583:Electrons; D007700:Kinetics; D009991:Oscillometry; D012680:Sensitivity and Specificity