Selection of intense spectral region and attosecond pulse from X2+ by using chirp-delay effect

A potential scheme to obtain intense harmonic spectra from X[Formula: see text] ([Formula: see text] and T) has been studied by using chirped-delay effect and half-cycle pulse. First, for the shorter pulse duration case, the main contributions of harmonic spectra of H[Formula: see text] and T[Formula: see text] are both coming from the falling part of laser field. While, for the longer pulse duration case, the rising and falling parts of laser field play the main role in harmonic spectra of H[Formula: see text] and T[Formula: see text], respectively. Second, according to the changed law of harmonic yields of H[Formula: see text] and T[Formula: see text] and by properly introducing the chirp-delay effect at some specific timing, the intense harmonic emission peak (HEP) can be obtained from both H[Formula: see text] and T[Formula: see text]. Third, with the help of the half-cycle pulse, the selected HEP can be further extended, showing the intense and broad spectral continua. Finally, by Fourier transformation of some harmonics on the spectral continua, the intense attosecond pulses with durations of 35 as can be produced.