Beyond the Orbital Shape Correlation of Molecular Tunnel Ionization: Impact of Permanent Polarizability and Higher Parabolic Channels on the Orientation Dependence

Molecular tunnel ionization sets the stage for the subsequent attosecond processes. Therefore, a comprehensive understanding of its dependence on various molecular properties, such as binding energy, wave function shape, dipole moment, and polarizability, is crucial for tailoring attosecond science concepts for scientific and technological applications. While the first three properties have been relatively well understood, the effects of polarizability have not been explored to the same extent in studies of molecular tunnel ionization. To address this gap, in this work we reveal the peak-shifting effect of permanent polarizability in tunnel ionization rates as the ionizing field varies. By analyzing a specially defined rate gradient, we determine the characteristic directions of the shift from the sign of the local slope of the gradient curve. Furthermore, we show how ionization into higher parabolic channels can transform minima of orientation-dependent rates into maxima. These findings demonstrate how the common assumption that the orientation dependence of tunneling rates resembles orbital shape can break down. We benchmark the method employed, the weak-field asymptotic theory (WFAT), and demonstrate good agreement with ab initio results, underscoring the efficiency and accuracy of WFAT in simulating strong-field ionization at low-to-moderate field strengths.