Theoretical investigation of alignment-dependent intense-field fragmentation of acetylene

We analyze the alignment-dependent dissociative and nondissociative ionization of acetylene, C2H2. Numerical models describing the yield of the singly and doubly charged ions (C2H2+, C2H22+) and several fragmentation and isomerization channels (C2H+ + H+, CH+ + CH+, CH2+ + C+) as a function of the relative alignment angle between the laser polarization axis and the molecular axis are presented. We apply and compare two different approaches. The first is based on time-dependent density functional theory. The second is a quasi-single-particle approach using the Dyson orbitals. We find good agreement between the results of both methods. A comparison of our theoretical predictions with experimental data allows us to show that the alignment-dependent yield of most reaction channels is described to high accuracy assuming sequential ionization. However, for some of the fragmentation channels, namely, CH+ + CH+ and C2H+ + H+, we find non-negligible influence of recollisional ionization.