Asymmetric molecular harmonic assisted generation of the attosecond X-ray pulse.

In this paper, we theoretically investigate the asymmetric molecular high-order harmonic emission and the attosecond X-ray pulse generation when the asymmetric molecular HeH2+ion is exposed to an intense chirped pulse. It is found that the molecular harmonics are strongly dependent on the internuclear distanceRas well as the chirp parameter, showing a smooth and intense harmonic plateau atR= 8.0 a.u. and β = 0.4. Further, by adding a subharmonic controlling pulse with the optimised conditions, a supercontinuum with a bandwidth of 602 eV can be obtained. Finally, by properly superposing the selected harmonics in the supercontinuum region, a series of isolated X-ray pulses with durations of sub-80 as are directly generated. [ABSTRACT FROM AUTHOR]