Molecular above-threshold-ionization angular distributions with attosecond bichromatic intense XUV laser pulses

Abstract

Angular distributions of molecular above-threshold ionization (MATI) in bichromatic attosecond extreme ultraviolet (XUV) linear polarization laser pulses have been theoretically investigated. Multiphoton ionization in a prealigned molecular ion H${}_{2}$${}^{+}$ produces clear MATI spectra which show a forward-backward asymmetry in angular and momentum distributions which is critically sensitive to the carrier envelope phase (CEP) $\ensuremath{\varphi}$, the time delay $\ensuremath{\Delta}\ensuremath{\tau}$ between the two laser pulses, and the photoelectron kinetic energies ${E}_{e}$. The features of the asymmetry in MATI angular distributions are described well by multiphoton perturbative ionization models. Phase differences of continuum electron wave functions can be extracted from the CEP $\ensuremath{\varphi}$ and time delay $\ensuremath{\Delta}\ensuremath{\tau}$ dependent ionization asymmetry ratio created by interfering multiphoton ionization pathways. At large internuclear distances MATI angular distributions exhibit more complex features due to laser-induced electron diffraction where continuum electron wavelengths are less than the internuclear distance.