Atomic hydrogen in a strong optical radiation field

Abstract

Experimental energy spectra and energy-resolved angular distributions of photoelectrons produced by multiphoton ionization of atomic hydrogen are presented for several wavelengths between 596 and 630 nm, peak intensities of about 10 W/cm, and laser pulse durations of about 0.5 ps.Resonant ionization processes via ac Stark-shift-induced resonances with excited states dominate the spectra. The results of Sturmian-Floquet calculations of these spectra and angular distributions are presented; they are in fair agreement with the experimental data.PACS number(s): 32.80.Rm, 42.50.Hz

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

“…Therefore, in order to observe pronounced oscillations of the partial ionization rates in higher photon channels (as found numerically in results of Refs. [25,26,[28][29][30][31][32] (27) and (28), one sees that a − b α β does not depend on c 1 , whereas α − iβ = det M − is 2 M 11 − 2ic 1 (M 22 − is 2 ) is a nonzero complex number in the limit c 1 → 0. Hence, one deduces that the second term in Eq.…”

“…[8,9,13,[25][26][27][28][29][30][31][32]). Note that for fixed parameters of the laser field, the amount of energy that has to be delivered in order to ionize a laser-dressed atom must be at least E min = −Re E + U p .…”

“…In the context of this work, it is essential to stress that a very thorough analysis of the ionization spectra of neutral atoms treated in the so-called single-active electron (SAE) approximation has been performed in a series of papers by Potvliege and Shakeshaft [25][26][27][28][29][30][31][32]. These papers present very detailed analyses of resonances that are induced when the atomic ground state and some excited states are shifted into multiphoton resonances by an intense laser field.…”

“…As discussed later on, the results presented in this paper and those of Refs. [23,[25][26][27][28][29][30][31][32] show the generality of the predicted effects. This paper is organized as follows.…”

Precision calculation of above-threshold multiphoton ionization in intense short-wavelength laser fields: The momentum-space approach and time-dependent generalized pseudospectral method

“…Extensive investigations have been performed both theoretically [11][12][13][14][15][16][17][18] and experimentally [7,12,14,[19][20][21][22][23][24][25][26][27][28][29][30][31] for a comprehensive understanding of the laser-induced atomic ATI for laser fields with wavelengths from visible lights (4×10 2 nm) to infrared radiations (1×10 5 nm). With the recent development of intense and ultrashort-wavelength free-electron lasers [32][33][34], the study of multiphoton * zyzhou@ku.edu † sichu@ku.edu processes in the high-frequency and strong-field regime becomes increasingly important [35][36][37].…”