Dependence of direct and rescattered photoelectron spectra of fluorine anions on orbital symmetry in a short laser pulse

We theoretically investigate the photoelectron spectra of fluorine anions by a few-cycle linearly polarized laser pulse for different atomic orbitals, which are calculated by an exact solution to the time-dependent Schr\"odinger equation and by the strong-field approximation, respectively. Through the comparison of results by both methods, we show that the initial orbital symmetry strongly affects the main shape of the photoelectron spectra. Based on the saddle-point method, we find that the orbital symmetry only affects the intracycle interference for the low-energy electron spectra. More importantly, it is found that the elastic scattering differential cross section leaves different fingerprints in the photoelectron spectra for atomic orbitals with different magnetic quantum numbers.