The Above Threshold Dissociation Dynamics Of HD+ In Ultrashort Pulse Laser Fields

With the development of ultrafast laser pulse technology, more and more theoretical and experimental researches focus on the interaction dynamics of atoms or molecules with laser fields. Especially, with the emergence of femtosecond laser techniques, many phenomena of the molecular dynamics can be detected and tracked at real time. Photochemistry pollution of aerosphere, destruction of ozonosphere, isotope separation by laser and gas aggradations of laser chemistry are all related to photodissociation. So photodissociation is one of the most significant phenomena. Because of the simplest molecular structure, H₂⁺ and its isotope HD⁺ have been investigated as benchmark systems in photodissociation research. The quantum wave packet dynamics calculations play an important role in explanation and anticipation of experimental results.The above threshold dissociation (ATD) of the HD⁺ molecular ion in femtosecond laser field is investigated theoretically by using a time-dependent quantum wave packet method in this paper. The key of the calculation is to solve the time-dependent Schr(o|¨)dinger equation. Based on the BOA, the wave packet is simultaneously propagated on the radiatively coupled 1sσand 2pσpotential energy curves. The photodissociation of HD⁺ has two dissociation channels: one channel HD⁺â†'D+H⁺ via 1sσstate, and the other channel HD⁺â†'H+D⁺ via 2pσstate. The initial wave function is found by using the Fourier grid Hamiltonian (FGH) method. The time propagation is accomplished by split operator method combined with fast Fourier transform (FFT) technique. The energy-dependent distributions of the dissociated fragments, resulting from multiphoton absorption above dissociation threshold, are calculated by an asymptotic-flow expression in the momentum space. Some parameters such as initial vibrational state, FWHM, length and intensity of laser field have some effects on the photondissociation, which can be seen from the energy-dependent distributions. The molecule dissociates primarily through absorption four photons for ground vibrational state and three photons for the first and second vibrational states. More photons are required to realize the dissociation of HD⁺ when FWHM, the laser wavelength and intensity increase. These dynamics phenomena are interpreted in terms of the concept of light-dressed potential.