Direct and sequential ejection of the two valence electrons of beryllium by ultrashort laser pulses with photon energies below 18.2 eV

Abstract

We investigate the two-photon double ionization of a beryllium atom by intense ultrashort laser pulses. We apply a nonperturbative approach to solve the time-dependent Schrödinger equation. We treat the atom as a two-active-electron system with two outer electrons in the field of a frozen core that includes the nucleus and the electrons of the 1s2 inner shell. We trigger the ionization with photon energies lower than the second ionization potential Ip(Be+(2s)) = 18.2 eV of the atom so that the 2s2 valence shell electrons can be directly ejected in the double continuum or sequentially ejected via excitation ionization through the Be+(2p) ion. We investigate, for various photon energies, the contribution of each of the direct and sequential processes to the ionization dynamic.

Double photoionization of the Be isoelectronic sequence

“…The gauge invariance (length and velocity) of our results has been checked. The double and single photoionization cross sections are extracted from formulas (23) and (24), respectively. For this approach Figure 3.…”

“…The diagonalization of equation ( 6) provides the eigenenergies and the expansion coefficients a c n, SLM of bound and continuum electronic states. More details about the efficiency of B-spline functions in the calculations of atomic and molecular field-free energy spectra are given in our previous works [18,19,[23][24][25].…”

Chirp-dependent ionization of hydrogen atoms in the presence of super-intense laser pulses*

“…For example, the chirped pulse can be used to explore the laser-matter interaction. [10][11][12][13][14][15] Especially, with the application of chirped pulse amplification (CPA) technique, [16] the intensity of laser can be dramatically increased.…”