Absolute single photoionization cross-sections of Br³⁺: experiment and theory

Abstract

Absolute single photoionization cross section measurements for Br 3+ ions are reported in the photon energy range 44.79-59.54 eV at a photon energy resolution of 21±3 meV. Measurements were performed at the Advanced Light Source at Lawrence Berkeley National Laboratory using the merged-beams technique. Numerous resonance features in the experimental spectrum are assigned and their energies and quantum defect values are tabulated. The crosssection measurements are also compared with Breit-Pauli R-matrix calculations with suitable agreement over the photon energy range investigated. Analysis of the measured spectrum including Rydberg resonance series identifications produced a new emperical determination of the ionizational potential of Br 3+ of 46.977±0.050 eV, which is 805 meV lower than the most recently published value of 47.782 eV. This disparity between our determination and the earlier published value is similar to an 843 meV shift in the accepted ionization potential published for iso-electronic Se 2+ as part of this same research program.

Single Photoionization Study of Br3+ via the Screening Constant by Unit Nuclear Charge Method

“…In Table 1 we quote the present SCUNC results for energy resonances (E), quantum defects (δ) and effective charge (Z * ) of the series due to 4p→nd transitions from the 1 D 2 excited states of Br 3+ converging to the 2 P 3/2 series limit in Br 4+ . It is seen that the data obtained compared very well with the experimental data of Macaluso et al, [15]. Up to n = 27, the energy differences relative to the experimental data is 0.000 eV which proves that the SCUNC method perfectly reproduces the experimental results.…”

“…In Tables 2 and 3 the present SCUNC data for energy resonances (E), quantum defects (δ) and effective charge (Z * ) respectively for the Rydberg series due to the 4p→nd transitions from the 3 P 2 and from the 3 P 1 excited states of Br 3+ converging to the 2 P 3/2 series limit in Br 4+ are listed. Comparison indicates excellent agreements with the ALS measurements [15]. In Table 3, the energy differences have never overrun 0.001 eV.…”

“…So, for the Br 3+ ions, Z core = 4 and f 2 = (35 − 4) = 31.0. The remaining f 1 -parameter is to be evaluated empirically using the ALS data of Macaluso et al, [15] for a given ( 2S+1 L J ) µl level with ν = 0. The empirical procedure of the determination of the f 1 -screening constant along with the corresponding has been explained in details in our previous works [11][12][13][14][16][17][18]].…”

“…In Section 2, we present a brief outline of the theoretical part of the work. The presentation and the discussion of the results obtained are given in Section 3 where comparisons are made with the available ALS experimental data [15]. In Section 4 we summarize our study and draw conclusions.…”

“…For Z > 30, neutron (n)-capture elements (e.g., Se, Kr, Br, Xe, Rb, Ba and Pb) produced by slow or rapid n-capture nucleosynthesis [5,6] have been detected in a large number of ionized nebulae [5,7,8]. For the Br 3 + ion, absolute single photoionization cross-section measurements were performed at ALS and numerous Rydberg series due to the 4p→nd and 4s→np transitions have been identified [15]. As stated by Kim and Mason [10], an important task for the atomic physics community is to provide data for photoionization for modeling of plasma and astrophysical systems.…”