Calculating strong-field, momentum-resolved photoelectron spectra (PES) from numerical solutions of the time-dependent Schr\"odinger equation (TDSE) is a very demanding task due to the large spatial excursions and drifts of electrons in intense laser fields. The time-dependent surface flux (t-SURFF) method for the calculation of PES [L. Tao, A. Scrinzi, New Journal of Physics 14, 013021 (2012)] allows to keep the numerical grid much smaller than the space over which the wavefunction would be spread at the end of the laser pulse. We present an implementation of the t-SURFF method in the well established TDSE-solver Qprop [D. Bauer, P. Koval, Comput. Phys. Commun. 174, 396 (2006)]. Qprop efficiently propagates wavefunctions for single-active electron systems with spherically symmetric binding potentials in classical, linearly (along $z$) or elliptically (in the $xy$-plane) polarized laser fields in dipole approximation. Its combination with t-SURFF makes the simulation of PES feasible in cases where it is just too expensive to keep the entire wavefunction on the numerical grid, e.g., in the long-wavelength or long-pulse regime.Comment: 29 pages, 5 figures, elsarticle style, code available at www.qprop.de. in Computer Physics Communications, available online since 27 June 201

Joint electron-ion energy spectra for the dissociative ionization of a model H + 2 in few-cycle, infrared laser pulses are calculated via the numerical ab initio solution of the time-dependent Schrödinger equation. A strong, pulse-dependent modulation of the ionization probability for certain values of the protons' kinetic energy (but almost independent of the electron's energy) is observed. With the help of models with frozen ions, this featurewhich mistakenly might be attributed to vibrational excitations-is traced back to the transient population of electronically excited states, followed by ionization. This assertion is further corroborated employing a twolevel model incorporating strong-field ionization from the excited state.