Gumberidze, A.

Lestinsky, M.

Rozenbaum, E.

Sosnova, K.

Stöhlker, T.

Trotsenko, S.

GSI Repository

Two-electron one-photon transition in Li-like BiS.Trotsenko1,2, A. Gumberidze3, K. Sosnova4, E. Rozenbaum4, M. Lestinsky2, and Th. Sto¨hlker1,2,51Helmholtz-Institut Jena, Jena, Germany; 2GSI, Darmstadt, Germany; 3ExtreMe Matter Institute/GSI, Darmstadt,Germany; 4Sankt-Petersburg University, Sankt-Petersburg, Russia; 5Friedrich-Schiller-University Jena, GermanyWe report on experimental study of the decay proper-ties of 1s(2s2) state in Li-like bismuth (Z=83), adopting astate selective K-shell ionization technique [1]. This stateis expected to undergo predominantly an exotic 1s(2s)2 →(1s)22p1/2 two-electron one-photon decay (TEOP) [2, 3],which is interesting because of its sensitivity to electroncorrelation effects. In the high-Z ions the 1s(2s2) statecan also decay to the ground (1s)22s state via a radiativemagnetic dipole M1-transition. The strong variation of thedecay properties of the states along the isoelectronic se-quence is an ideal testing ground for our understanding ofthe interplay of electron correlation and relativistic effectsin a few-electron ions. The experiment was performed atFigure 1: Preliminary x-ray spectra recorded forBi79+ → N2 (see text for details).the ESR (GSI) with 98 MeV/u Be-like bismuth ions collid-ing with a gas jet target (N2). The x-rays produced in thisprocess (see Fig. 1) were measured under an angle of 35◦with respect to the propagation direction of the ion beam(for details concerning the setup see [1]). By the coinci-dent registration of x-rays with the charge state of the ionsafter the collision, few different radiative processes can beseparated: K-shell excitation of the Be-like ions, the radia-tive electron capture and the formation of excited states ofthe Li-like ions produced by K-shell ionization. As can beFigure 2: Preliminary analysed ionization spectrum peak;blue steps / blue line: the peak position defined by radiativesources calibration/ the corresponding fitting curve; blacksteps / black line: the peak position obtained by the cali-bration based on the theoretical Kα1 and Kα2 lines / thecorresponding fitting curve; grey boxes: theoretical predic-tions for the TEOP (left) and M1 (right) transitions withthe widths corresponding to the theoretical uncertainties;red line: convolution of the theoretical predictions [3].seen in the ionization spectrum (Fig 1:Ionization), K-shellionization appears to be a very selective population pro-cess, because in the associated photon spectrum only onesingle x-ray line is observed stemming from the decay ofthe 1s(2s2) state.The energy separation between the two transitions of in-terest, TEOP[1s(2s2) → (1s)22p1/2] and M1[1s(2s2) →(1s)22s1/2], is close to 250 eV in the emitter frame. Due tothe lack of high resolution x-ray detectors within the cur-rent investigation, the goal of the current data analysis is todetermine M1/TEOP branching ratio, i.e. the contamina-tion of the TEOP by the M1 decay, using an accurate linecentroid determination of the observed x-ray line. Apartfrom a conventional method utilising an accurate calibra-tion of the detector with radioactive sources, a complemen-tary calibration method was used based on correspondingenergies of the Kα1- and Kα2-lines, produced by excita-tion (Fig. 1:Excitation), as an energy reference. The latterprovides an important cross-check for the Doppler correc-tions to be applied. This, however, is based on the assump-tion that K-shell excitation of the Be-like ions occurs tothe 1s(2s)2p3/2 and 1s(2s)2p1/2 levels exclusively. Pre-liminary results are presented in the Fig. 2, suggesting adominance of the TEOP over the M1 transition. The dataanalysis is in progress.References[1] J. Rzadkiewicz et al., Phys. Rev. A 74, 012511 (2006)[2] C. Z. Dong et al., J. Phys. B: At. M. Op. Ph. 39, 3121 (2006).[3] A. Volotka and Y. Kozhedub, Private communication.PNI-INHOUSE-EXP-02 GSI SCIENTIFIC REPORT 2012370

Two-electron one-photon transition in Li-like Bi

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Two-electron one-photon transition in Li-like Bi

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