STSM by Philipp Marquetand, University of Vienna (AT)  with Tamas Rozgonyi, Hungarian Academy of Sciences (HU)
On July 2nd, 2015 (8 days)

Strong-Field Ionization Simulations Using Adiabatic Elimination

Strong-field ionization including multiphoton transitions is hardly understood yet due to the complex interplay of intermediate resonant states, their dynamic Stark shift, the ponderomotive potential and many more fundamental processes. In order to obtain nonetheless a simple and more intuitive picture, we have developed a theoretical description and a corresponding code, which makes use of two main approximations. All off-resonant intermediate states are not treated explicitly but removed by adiabatic elimination (ADEL) from the system of equations of motion. Furthermore, the ionization continuum is represented by a Legendre-polynomial based discretization approach.

In this STSM, we extended our code to include non-adiabatic coupling between multiple intermediate resonant states. In this way, we are able to test a hypothesis developed by our experimental partner, Thomas Weinacht (Stony Brook University), that such vibrational couplings are at the origin of some of the peaks in the photo-electron spectrum of Iodobromomethane. We have tested our new implementations, comparing a 0-dimensional, a 1-dimensional and our new 1-dimensional code with couplings. First simulations on a model with arbitrarily chosen parameters show that indeed non-adiabatic couplings can lead to additional peaks in the photo-electron spectrum, see Fig. 1. The model consists of a ground state |0>, two intermediate resonant states |i1>, |i2> and two electronic continua |c1>, |c2>. The states |0> and |i1> are coupled via a 5-photon process, while the states |i1> and |c1> as well as |i2> and |c2> are coupled via a 2-photon process, respectively. A non-adiabatic coupling between |i1> and |i2> can be switched on and off. If the coupling is present, an additional peak appears in the photo-electron spectrum.


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