Attosecond photoelectron microscopy of H-2( )

作者：Hu S X^*; Collins L A; Schneider B I

来源：Physical Review A, 2009, 80(2): 023426.

DOI：10.1103/PhysRevA.80.023426

We present a numerical study of the ultrafast ionization dynamics of H-2(+) exposed to attosecond extreme ultraviolet (xuv) pulses that goes beyond the Born-Openheimer approximation. The four-dimensional, time-dependent Schrodinger equation was solved using a generalization of the finite-element discrete-variable-representation/real-space-product technique used in our previous calculations to include the dynamical motion of the nuclei. This has enabled us to expose the target to any polarized light at arbitrary angles with respect to the molecular axis. Calculations have been performed at different angles and photon energies ((h) over bar omega = 50 eV up to 630 eV) to investigate the energy and orientation dependence of the photoionization probability. A strong orientation dependence of the photoionization probability of H-2(+) was found at a photon energy of (h) over bar omega = 50 eV. At this energy, we found that the ionization probability is three times larger in the perpendicular polarization than in the parallel case. These observations are explained by the different geometric "cross sections" seen by the photoejected electron as it leaves the molecule. This ionization anisotropy vanishes at the higher-photon energy of (h) over bar omega >= 170 eV. When these higher-energy xuv pulses are polarized perpendicular to the internuclear axis, a "double-slit-like" interference pattern is observed. However, we find that the diffraction angle only approaches the classical formula phi(n)= sin(-1) (n lambda(e)/R-0), where n is the diffraction order, lambda(e) is the released electron wavelength, and R-0 is the internuclear distance, when n lambda(e) becomes less than 65% of R-0. These results illustrate the possibility of employing attosecond pulses to perform photoelectron microscopy of molecules.

• 出版日期2009-8
• 单位国家自然科学基金委员会