We study the Rabi flopping of the population between the ground and excited 2p states of the hydrogen atom, induced by intense short laser pulses of different shapes and of carrier frequency $\omega =0.375$ a.u. which resonantly couples the two states, and manifestations of this dynamics in the energy spectra of photoelectrons produced in the subsequent ionization of the atom from the excited state. It is found that, for Gaussian, half-Gaussian and rectangular pulses, characterized by the same pulse area, the final populations take the same values and the spectra consist of similar patterns having the same number of peaks and approximately the same separation between the prominent edge (Autler–Townes) peaks. The additional analysis in terms of dressed states showed that the mechanism of formation of multiple-peak structures during the photoionization process is the same regardless of the pulse shape. These facts disprove the hypothesis proposed in earlier studies with Gaussian pulse, that the multiple-peak pattern appears due to dynamic interference of the photoelectrons emitted with a time delay at the rising and falling sides of the pulse, since the hypothesis is not applicable to either a half-Gaussian pulse that has no rising part or a rectangular pulse whose intensity is constant.

A method for determining the resonant dynamic Stark shift (RDSS), based on wave-packet calculations of the populations of quantum states, is presented. It is almost insensitive to variations of the laser pulse profile, and this feature ensures generality in applications. This method is used to determine an RDSS data set for 3s → nl (n ≤ 6) transitions in sodium induced by laser pulses with peak intensities up to 7.9 × 10¹² W cm⁻² and wavelengths in the range from 455.6 to 1139 nm. The data are applied to analyze the photoelectron spectra (electron yield versus excess energy) of the sodium atom interacting with 800 nm laser radiation. Substructures observed in the experimentally measured spectra are successfully reproduced and related to the resonantly enhanced multiphoton ionization via specific (P and F) intermediate states.

Atomic and molecular (A&M) databases that contain information about species, their identities and radiative/collisional processes are essential and helpful tools that are utilized in many fields of physics, chemistry, and chem/phys-informatics.