Theoretical Study Of Tunneling Ionization For Asymmetric Linear Molecules In An Intense Laser Field~1

A series of interesting nonlinear phenomena,such as high-energy above-threshold ionization?HATI?,non-sequential double ionization?NSDI?and high-order harmonic generation?HHG?,will generate by the interaction of an intense laser pulse with molecules.Tunneling ionization of molecules is the first step of these strong-field phenomena.By studying the orientation-dependent ionization rates,we can know the symmetry of molecular orbital.This imaging method is much more direct and simple compared with the tomographic imaging technique.Theoretically,the molecular ionization rate can be obtained by solving time-dependent Schr?dinger equation?TDSE?based on single-active-electron?SAE?approximation or by using the time-dependent density functional theory?TDDFT?.Nevertheless,the above-mentioned methods are very time-consuming.As a result,Some simpler theoretical models are approved and desirable.For instance,molecular Ammosov-Delone-Krainov?MO-ADK?and molecular strong-field approximation?MO-SFA?.The MO-ADK model has been widely applied to study the tunneling ionization of molecules due to its many advantages,such as the simple analytic formula about ionization rate and the favorable accuracy in the tunneling region.The Keldysh parameter?is very important to distinguish different ionization mechanisms.When??29?1,multi-photon ionization will prevail;if??27?1,tunneling ionization is dominant.In this paper,we mainly calculate the accurate structure parameters of asymmetric linear molecules for the MO-ADK model.It is the first step that one-electron potentials of linear molecules are numerically constructed using the Leeuwen-Baerends?LB??model.Then the molecular wave functions with the correct asymptotic behavior are obtained by solving the time-independent Schr?dinger equation?TIDSE?with B-spline functions.In the MO-ADK model,the accurate structure parameters C_lm of the highest occupied molecular orbital?HOMO?of 123 linear molecules are determined and tabulated for the future applications.On the other hand,we also calculate the photoelectron energy spectrum of hydrogen by using the window-operator technique?WOT?.The most advantage of the WOT is to avoid the calculations of continuum eigenstates of atoms by comparing with the projection technique?PT?.