Origin of the double-peak structure in longitudinal momentum distributions for single ionization of an He atom in strong laser field

Abstract

The single ionization of an He atom by intense linearly polarized laser field in the tunneling regime is studied by S-matrix theory. When only the first term of the expansion of the S matrix is considered and time, spatial distribution, and fluctuation of the laser pulse are taken into account, the obtained momentum distribution in the polarization direction of laser field is consistent with the semiclassical calculation, which only considers tunneling and the interaction between the free electron and external field. When the second term, which includes the interaction between the core and the free electron, is considered, the momentum distribution shows a complex multipeak structure with the central minimum and the positions of some peaks are independent of the intensity in some intensity regime, which is consistent with the recent experimental result. Based on our analysis, we found that the structures observed in the momentum distribution of an He atom are attributed to the "soft" collision of the tunneled electron with the core.

Recursive algorithm for arrays of generalized Bessel functions: Numerical access to Dirac-Volkov solutions

“…A fast and reliable numerical evaluation of J n (x, y) would also speed up calculation of wave packet evolution in laser fields [17,18]. In nonrelativistic calculations, the generalized Bessel function has been employed mainly for strong-field ionization [19,20,21,22], but also for high-harmonic generation [23,24]. On the mathematical side, a thorough study of J n (x, y) has been initiated in a series of papers [25,26,27], and even further generalizations of the Bessel function to multiple arguments and indices have been considered [28,29,30,31].…”

Instantaneous multiphoton ionization rate and initial distribution of electron momentum

“…Nevertheless, a dip at the origin has been observed experimentally [23,24] in the parallel-momentum distribution for the nobel gases within the tunneling regime, and afterwards it has been investigated theoretically in Ref. [25] and references therein. However, such a phenomenon is beyond Eq.…”

Scaling of the Low-Energy Structure in Above-Threshold Ionization in the Tunneling Regime: Theory and Experiment

“…Several explanations have been proposed and are still under debate, tracing the effect to the long-range Coulomb potential [14][15][16], Freeman resonances [17,18], or the persistence of ATI peaks in the tunneling regime [19,20]. Recently, another unexpected low-energy structure (LES) has been reported in the ATI electron-energy distribution, which becomes most significant at longer wavelength or decreasing γ < 1 [21,22].…”