Implications of configuration interaction wavefunctions in length and velocity theoretical determination of generalized oscillator strengths for the excitations to 2p5(3d, 4s, 4d, 4f) of neon

Abstract

The generalized oscillator strengths (GOSs) of 2p5(3d,4s, 4d, 4f) states excited from neon ground state, are studied by the configuration interaction (C I) method and the random phase approximation with exchange (RPAE). Wavefunctions of these states obtained from the configuration interaction code CIV3 of Hibbert are employed to compute these GOSs. We report results of calculations for both the velocity and length formulations of the GOS for the neon transitions 2p6 → 2p54s, 2p6 → 2p5(3d,4d) and 2p6 → 2p54f respectively for multipole strengths ℓ = 1, ℓ = 1, 3 and ℓ = 2, 4 respectively. The results show remarkable agreement among the extrema positions resulting from the velocity and length forms despite the rather different absolute values of GOS they reveal. This work reduces significantly the difference between the extrema positions of the GOS obtained in the theoretical calculations of Amusia et al. and those experimentally found by Chen et al. for dipole 2p6 → 2p54s transition. The profiles of our calculated GOS are in agreement with the theoretical results of Amusia et al. In the present work, for the 2p6 → 2p5(3d,4d) transitions, our length dipole RPAE GOS curves agree with the pictures obtained from the data RPAE GOS of Amusia et al. while the length octupole GOS have values smaller than those of the Amusia et al. GOS results except in the small squared transferred momentum K2 region. Good agreement between our length RPAE GOS and the recent RPAE results of Amusia et al. is found for the quadrupole excitation to 2p54f. The results of length and velocity hexadecapole GOS are comparable with each other for the same transition, and experimental work is needed. The present calculations also reveal that the electron correlations effects are noticeable around the region of the GOS maxima.