Cooper minimum in singly ionized and neutral argon

Abstract

We present an analysis of the appearance of the Cooper Minimum in singly ionized argon in both the photoionization cross-section (PICS) and high-harmonic generation (HHG) spectrum. We employ two computational approaches based on the same R-matrix technique to provide a coherent description of the atomic structure of the Ar + system, finding that the PICS and HHG spectrum are affected differently by the inclusion of additional residual ion states and the improved description of correlation effects. Both the PICS and HHG spectrum possess a clear minimum for all atomic structure models used, with the centre of the minimum at 55 eV in the PICS and 60 eV in the HHG spectrum for the most complete description employed. The HHG minimum is systematically shifted to higher energies with respect to the PICS minimum. We also find that the initial magnetic alignment (magnetic quantum number) of the Ar + system does not affect substantially the position and shape of the HHG minimum (given a sufficiently detailed atomic structure description), but the harmonic yield is enhanced by two-orders of magnitude for ML = 1 over ML = 0. We also perform similar calculations for neutral argon, finding that this system is more sensitive to enhancements in the atomic structure description.PACS numbers: 32.80. Rm, 42.65.Ky

Detecting the minimum in argon high-harmonic generation spectrum using Gaussian basis sets

“…Argon atom is well known to show a Cooper minimum in the HHG spectrum [15][16][17][18], nearly independent on the applied intensity and due to its electronic structure. Under slightly different experimental conditions, the energy corresponding to the minimum in HHG spectrum has been found to span the range 48-54 eV [15,17,19].…”

Photoelectron spectra of argon in circularly polarized pulses studied by atom-Volkov strong-field approximation

“…There are intensive interests in the topic [23,30,34,35]. Argon has six valence electrons and the SAE is a simplified model potential [36]. We demonstrate the Cooper minimum of photoionization by TDSE simulations of 27 nm and 54 nm CP pulses.…”

Core-resonance line-shape analysis of atoms undergoing strong-field ionization

“…RMT is a fully non-perturbative, ab initio approach to solve the TDSE for multi-electron atoms and molecules driven by short, intense laser pulses. The RMT calculations employ a non-relativistic description of the Xe atom [33], comprising Hartree-Fock orbitals up to the 5p, and all 4d −1 ϵℓ, 5s −1 ϵℓ and 5p −1 ϵℓ continuum channels up to a maximum total angular momentum of 40. The NIR pulse has a central wavelength of 760 nm with a Gaussian envelope (FWHM 4.5 fs).…”