High angular momentum 6pnl and 6dnl doubly excited Rydberg states of barium

Abstract

6p3,,nl(n=1lto15, 1=5ton-I)and6d,,,nl(n=Il to 14,1=6ton-I)doubly excited Rydherg states of barium have been studied using a multistep laser excitation technique. The excitation is via the hound 6s,,,nl states which are populated using an electric-field switching method which allows us the selective population of high-l angular momentum states. The resulting spectra clearly demonstrate the presence of dielectronic correlation. We show that this correlation is well described in terms ofthe ( j -I)K coupling scheme, taking into account in a perturbalive way the dipole and quadrupole interadion terms.

CW laser spectroscopy of autoionising 6p 3/2 nl states of Barium

“…It should be noted that the calculated oscillator strength distributions do not directly correspond to the measured peak heights due to the different autoionisation rates for the different K-components. The calculated relative energies and intensities of the observed K-components compare well with the low-n (n"7-13) members of the 6p nh states investigated by Bente and Hogervorst [2] and Pruvost et al [4]. The quantum defects of the 6p 40h K-states are slightly larger than the quantum defects for the low-n states close to the 6p -limit observed by Bente and Hogervorst [2].…”

“…The quantum defects of the 6p 40h K-states are slightly larger than the quantum defects for the low-n states close to the 6p -limit observed by Bente and Hogervorst [2]. Their quantum defects for the low-n members differ significantly from the quantum defects for the same states calculated by Pruvost et al [4]. It has to be noted that these calculated quantum defects were derived with a model potential to determine the Ba> matrix element 16p"r"6p2.…”

“…The matrix element 16p"r"6p2 has been calculated by Jaffe et al [16] and Pruvost et al [4] and is given in Table 2. The hydrogenic value of 1nl"r\"nl2 equals (n(l#1) (l#1/2) l)\ [15].…”

“…As shown in Table 1 the calculated multiplet splitting with the matrix element of Jaffe et al [16] compares best with the experimental values. Pruvost et al [4] did not report accurate experimental data to compare energies of resonances. The calculated positions and intensities of the K-components are in good agreement with the experimental data, confirming our assignment.…”

“…The studies on doubly-excited Rydberg states of alkaline-earth atoms partly focus on the understanding of autoionisation processes [1][2][3][4][5][6] and partly on effects of correlated electron motion [7][8][9][10][11]. High angular momentum Rydberg states received special attention as in this case the Rydberg electron does not penetrate the orbit of the inner (excited) electron, thus reducing autoionisation rates.…”