(color online) Chirp dependence of (a) photoelectron energy spectra; (b), (c) photoelectron angular distributions at different photoelectron energies; and (d) total population of excited bound states of H. The orders of the ATI peaks are (b) S = 1 and (c) S = 2 as labeled in (a). We consider three different chirp rates, i.e., ξ = −1.73 (solid), ξ = 0 (dashed), and ξ = 1.73 (dot-dashed). The single photon energy is 15.5 eV.