Threshold-Related Enhancement of the High-Energy Plateau in Above-Threshold Detachment

Threshold effects in strong-field ionization: Energy shifts and Rydberg structures

“…These experiments have stimulated a number of theoretical efforts aimed at identifying the origin of this effect. Especially intriguing was the discovery that similar enhancements are observed in the ATD process, in which atomic negative ions, instead of neutral atoms, are detached by a laser field [2][3][4][5][6][7][8][9][10][11][12][13]. Based on model calculations employing zero-and finite-range potentials, it was realized that the aforementioned enhancements stem from the behaviors of detachment yields at multiphoton thresholds, which are consistent with predictions of the Wigner threshold law [22].…”

“…While threshold effects in ATD are very well understood and confirmed by numerous calculations [2][3][4][5][6][7][8][9][10][11][12][13], similar recent studies devoted to abovethreshold ionization (ATI) or to high-harmonic generation (HHG) (a competing process) reach different conclusions (see, e.g., Refs. [14][15][16]).…”

“…Theoretical analyses of the role of threshold laws in abovethreshold detachment (ATD) by strong laser fields have been carried out in many works [2][3][4][5][6][7][8][9][10][11][12][13]. While threshold effects in ATD are very well understood and confirmed by numerous calculations [2][3][4][5][6][7][8][9][10][11][12][13], similar recent studies devoted to abovethreshold ionization (ATI) or to high-harmonic generation (HHG) (a competing process) reach different conclusions (see, e.g., Refs.…”

Cutoffs of high-energy plateaux for atomic processes in an intense elliptically polarized laser field

“…Then, replacing the function fe(t) by a single harmonic, f e (t) ~ exp(-2ik c ωt), we handle the integral over t in (2) using the saddle point method, where the saddle points t s are given by (14) The maximum value of p n corresponds to the minimum real value of t s . For electron ejection along the major axis of the polarization ellipse, p n,max is given by (15) As shown in fi gure 2(a), the estimate (15) agrees reasonably well with the exact results for a ZRP model (calculated similarly to those in [18]; note that, e.g., for Kr (|E 0 | ≈ 14.0 eV) these results as well as those in fi gure 1 correspond to ω ≈ 1.79 eV and I ≈ 3.5 × 10 15 W cm -2 ). The rapid decrease of the average plateau heights in fi gure 2(a) with decreasing originates from the similar decrease of f 2k in fi gure 1(a).…”

“…Using (17), the integral over t in the amplitude (2) may be estimated by the saddle point method, where the saddle points, t = t i (i = 1, 2, ...), are given by (18) Analysis shows that the amplitude (2) oscillates as a function of n for real values of t i and has an exponential smallness for complex t i . Thus the position of the K-plateau cutoff corresponds to the minimum value of p n at which the roots t i of equation (18) acquire an imaginary part.…”