Study On The Generation Of High-order Harmonic And Isolated Attosecond Pulses Of Atom In The Chirped-Laser Field

The development of attosecond technology is one of the most significant achievementin the field of ultrafast optics. Not only have it been greatly promoting the spectroscopic andthe measurement of time resolution, realizing the dream of steering and tracing of theelectron dynamic processes in atoms and molecules. The scientists were looking for someefficient methods to achieve shorter and shorter attosecond pulses over the past decade.Since the high-order harmonic spectrum can be extended to the soft X-ray region and exhibita supercontinuous structure, it become a preferred source for the generation of attosecondpulses in the experiment. Such ultrashort attosecond pulses can be produced from theharmonics of gas-phase atom with different techniques, including polarization gating,two-colour gating and ionization gating. Theoretically, the attosecond pulse can be generatedby superposing several harmonics of atoms exposed to an intense laser fields by solving thetime-dependent Schr dinger equation.In recent years, people are more interested in studies of laser-molecular interactions,this is because of intense laser and molecular interactions in the process not only canappear and atomic system the same phenomenon, and there will be some more complex,interesting physical process. As bond-softening, bond-hardening, above-thresholddissociation, charge-resonance-enhanced ionization and the Coulomb explosionphenomenon. Similarly, the theory of these phenomena is mainly the numerical solution ofmolecules in the intense laser fields of time-dependent Schrodinger equation.The major investigations are listed as follows:Firstly, we proposed an efficient method to generate an ultrashort attosecond pulsewhen a model He is exposed an intense few-cycle chirped laser pulse and a half cycle pulse.By solving the time-dependent Schr dinger equation numerically with split-operator method,we found that the harmonic energy can be extended effectively to I p+21.6Up.The singleattosecond pulses can be obtained by superposing several harmonics from different regionsof the plateau, the shortest attosecond pulse can reach37as. Furthermore, to understand thephysical mechanics of the emission of high-order harmonics, the classical analysis and thetime-frequency analysis have been performed. Secondly, Based on our upcoming about intense laser and molecular interactions ofwork, Energy levels and wavefunctions of the hydrogen and the hydrogen molecular ion arecalculated by solving stationary Schr dinger equation with B-splines functions based on thesingle-center expansion approach. By adopting nuclear positions as knots of B-splines basis,high-precision molecular orbital energies can be obtained.