Alignment effects in two-photon double ionization of H2in femtosecond xuv laser pulses

Abstract

Triple-differential cross sections for two-photon double ionization of the aligned hydrogen molecule at the equilibrium distance are presented for a central photon energy of 30 eV. The temporal response of the laser-driven molecule is investigated by solving the time-dependent Schrödinger equation in full dimensionality using two-center elliptical coordinates and a finite-element discrete-variablerepresentation approach. The molecular orientation is found to have a strong effect on the emission modes of the two correlated photoelectrons. This molecular effect is most noticeable when the molecular axis and the laser polarization vector are oriented parallel to each other. For intermediate cases between the parallel and perpendicular geometries, the dominant emission modes for twoelectron ejection oscillate between those for the two extreme cases. The contributions from different ionization channels are also analyzed in detail. Depending on the emission direction of the reference electron, the interference contributions from the various channels can be constructive or destructive at small alignment angles, while they always contribute constructively to the triple-differential cross sections near the perpendicular geometry.

Resonance effects in two-photon double ionization of H2by femtosecond XUV laser pulses

“…Both the discrepancies between various calculations and the molecular effects are most noticeable when the molecular axis and the laser polarization vector are oriented parallel to each other [12]. However, for the same or very similar laser parameters (pulse duration and peak intensity), we emphasize that the two recent calculations of Simonsen et al [13] and Ivanov and Kheifets [14] show good agreement with our previous results [11] in terms of the angle-integrated and angle-resolved cross sections, respectively.…”

The quantum chemistry of attosecond molecular science

“…This limitation can be partially overcome by using polynomial spherical Gaussian type orbitals, but for many applications the number of oscillations in the calculated wave function is not large enough. For small systems, mainly and H 2 , methods based on B‐spline basis functions or finite elements discrete variable representations (FE‐DVR) have been developed . These basis functions allow for a very accurate representation of the continuum wave functions up to very long distances.…”

“…Equation ( 1) is a nonseparable differential equation of second order in the 3N and 3M electronic and nuclear coordinates and of first order in time. By solving this equation in a grid, nearly exact solutions have been obtained in the center-of-mass frame for the H + 2 molecular ion (N = 1, M = 2) [28][29][30][31][32][33][34][35][36][37][38][39] and H 2 (N = 2, M = 2), in the latter case for specific molecular orientations (i.e., by neglecting molecular rotations). 40,41 However, such methods are inapplicable to larger molecular systems due to their high computational cost.…”

“…For small systems, mainly H + 2 and H 2 , methods based on B-spline basis functions [40][41][42]47,70,71 or finite elements discrete variable representations (FE-DVR) have been developed. 34,38,39,72 These basis functions allow for a very accurate representation of the continuum wave functions up to very long distances. In particular, Bsplines can do the job because they are piecewise polynomial functions defined over an interval [0, R max ], where R max can be as large as desired, divided in subintervals by a grid of knots 42,73 (see Figure 3b).…”

Two-photon double ionization of metastable1,3S1s2shelium

“…Being the simplest two-electron system, * aleksander.simonsen@ift.uib.no † morten.forre@ift.uib.no helium was the first target of considerable theoretical [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] and experimental [26][27][28][29][30][31] interest. Other two-electron systems have also been investigated, including TPDI of fixed-in-space H 2 [32][33][34][35][36][37][38].…”