Angle-dependent molecular above-threshold ionization with ultrashort intense linearly and circularly polarized laser pulses

Abstract

We present molecular above-threshold ionization (MATI) spectra generated by ultrashort intense linearly and circularly polarized laser pulses from nonperturbative numerical solutions of the corresponding time-dependent Schr\"odinger equation in the molecular-ion ${{\mathrm{H}}_{2}}^{+}$. It is found that high-order MATI spectra with maximum kinetic energy $32{U}_{p}$, where ${U}_{p}={I}_{0}/4{m}_{e}{\ensuremath{\omega}}_{0}^{2}$ is the ponderomotive energy at intensity ${I}_{0}$ and frequency ${\ensuremath{\omega}}_{0}$, can be obtained in ${{\mathrm{H}}_{2}}^{+}$ at great internuclear distances $R$ for both linear and circular polarizations. Quasiclassical laser-induced collision models confirm that such high-order MATIs mainly result from a collision with neighboring ions of the ionized electron. Interference patterns in the high-order MATI spectra are critically sensitive to both the internuclear distance $R$ of the molecules and the polarizations of the driving laser pulses. Moreover, with few-cycle laser pulses, the carrier-envelope phase sensitivity of MATI angular distributions is also investigated for varying internuclear distances $R$. At critical internuclear distances for charge-resonance-enhanced ionization, we also find that enhanced interference patterns occur.