Multicenter effect in high-order above-threshold ionization of polyatomic molecules

The multicenter nature of molecules can affect the strong field ionization. By studying the resonancelike enhancement structure in the high-order ATI spectrum of C2H4 and C2H6, we illustrate how the multicenter effect contributes to the molecular tunneling ionization. We find the hydrogen contributions lead to the weak resonance-like structure of C2H6 but have no affect for C2H4, this target dependence origins from their different HOMO structures. Those conclusions are supported by Strong Field Approximation calculation.