Comment on Detailed instantaneous ionization rate of H2+ in an intense laser field

The quantity '' component instantaneous ionization rate '' introduced by M. Vafaee et al. [Phys. Rev. A 74, 043416 (2006)] for the analysis of ionization of H-2(+) in intense laser pulses is discussed. It is shown that the meaning of this quantity as defined in that work is dubious, since there exists a lower time limit below which a quantum mechanical transition does not scale linearly in time and thus does not fulfill the requirements of a rate. Therefore, in a laser field it is impossible to define a rate with subcycle resolution. The analysis of a characteristic photoelectron spectrum reveals also that the '' instantaneous rate '' that is shown to be the electron flux through some boundary cannot be related to ionization without a deconvolution procedure. Finally, the '' negative ionization '' is identified as caused by the well-known quiver motion in strong laser fields.