Theoretical characterization of the collective resonance states underlying the xenon giant dipole resonance

Abstract

We present a detailed theoretical characterization of the two fundamental collective resonances underlying the xenon giant dipole resonance (GDR). This is achieved consistently by two complementary methods implemented within the framework of the configuration-interaction singles (CIS) theory. The first method accesses the resonance states by diagonalizing the many-electron Hamiltonian using the smooth exterior complex scaling technique. The second method involves a different application of the Gabor analysis to wave-packet dynamics. We identify one resonance at an excitation energy of 74 eV with a lifetime of 27 as and the second at 107 eV with a lifetime of 11 as. Our work provides a deeper understanding of the nature of the resonances associated with the GDR: a group of close-lying intrachannel resonances splits into two far-separated resonances through interchannel couplings involving the 4d electrons. The CIS approach allows a transparent interpretation of the two resonances as new collective modes. Due to the strong entanglement between the excited electron and the ionic core, the resonance wave functions are not dominated by any single particle-hole state. This gives rise to plasma-like collective oscillations of the 4d shell as a whole.

Attosecond delay of xenon4dphotoionization at the giant resonance and Cooper minimum

“…As a function of energy the real part is seen to turn around and sluice through zeros twice at around 80 eV and 101 eV. As characteristics of the collective resonant motions [31], the imaginary component also shows minima at these energies; qualitatively similar results were also recently obtained in the time-dependent configuration interaction singles (TDCIS) calculations [33]. The lower energy minimum is found significantly weak in TDLDA and its position coincides with the deep minimum of the LDA matrix element (also shown) at the LDA shape resonance (Fig.…”

“…This is a unique spectral feature largely originated from a manybody correlation driven collective process involving predominantly 10 inner electrons in the 4d subshell [30][31][32][33]. This feature is fundamentally different from noncollective, large resonances, such as, the 3p → 3d Auger in Mn [34].…”

Attosecond x-ray scattering from a particle-hole wave packet

“…It has been applied successfully in the investigation of many ultrafast processes in intense light pulses [29,44,46,47,67]. In this approach, the wave function of the many-body system is expanded in terms of the Hartree-Fock ground state of the system | 0 and 1-particle-1-hole (1p1h) excitations.…”

Time-dependent configuration-interaction-singles calculation of the 5p -subshell two-photon ionization cross section in xenon

“…The study revealed that two-photon ionization is a most sensitive tool to probe the effect of collective effects in the 4d shell. The electron correlation effects lead to two distinct resonance states constituting the giant dipole resonance [16] which cannot be attributed to single particle-hole states [17].…”