Spectral shape of two-photon decay from 2S state in He-like tin

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1 Spectral shape of two-photon decay from 2S state in He-like tin Team Ajay Kumar GSI, Darmstadt S. Trotsenko,2, D. Banas 3, H. Beyer, H. Bräuning,A. Gumberidze, S. Hagmann,2, S. Hess,2, P. Jagodziński 3, C. Kozhuharov, R. Reuschl,2,S. Salem, U. Spillmann,2, M. Trassinelli,4, A. Volotka 5, G. Weber,6, Th. Stöhlker,6 and the ESR-Team Atomic Physics Group, GSI-Darmstadt, Germany 2 IKF, University of Frankfurt, Germany 3 Institute of Physics, Swietokrzyska Academy, Kielce, Poland 4 Institut des NanoSciences de Paris, Campus Boucicaut, 7505 Paris, France 5 Institut für Theoretische Physik, TU Dresden, Germany 6 Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Germany 05-Feb-08 EAS, Riezlern

2 05-Feb-08 EAS, Riezlern 2 Outline Introduction and motivation Experimental details Data analysis and results Summary

3 Introduction and motivation Two-photon decay in He-like ions He-isosequence Single photon transition s2s S 0 s 2 S 0 E 0 E E2 s2s S 0 s 2 S 0 + E 0 0 = is forbidden J = J 0 Normalized intensity 3 2 He-like ion Z= Calculated photon energy distribution of 2 S 0 S 0 transition E x =E /E 0 =E 2 /E 0 s2s S 0 s 2 S 0 + E + E 2 Maria Göppert-Mayer Nobel Laureate, 963 E + E 2 = E 0 = E i -E f Two-photon (2E) decay or One-electron two-photon decay M. Göppert, Naturwissenschaften 7 (929) 932 M. Göppert-Mayer, Ann, Phys. 9 (93) 273 E x / E 0 Derevianko and Johnson, Phys. Rev. A 56 (997) Feb-08 EAS, Riezlern 3

4 05-Feb-08 EAS, Riezlern 4 Energy differential emission rate of two-photon decay A( E ) de E E M de 2 fi 2 < f D n >< n D2 i > < f D2 n >< n D i > M fi = + E + E E + E ni ni 2 A( E M de ) de f( f) fi 2.4 f = E E ; f = = f 2 2 E0 E0 Overall shape of the spectral distribution Total emission rates A T = 2 0 E if A ( E ) de Normalized intensity Photon energy fraction

5 Introduction and motivation Why going to highly charged high-z ions? 2 P 2 3 P 2 2 S P 0 E S 3 P ~Z 6 2E M ~Z 0 EM ~Z 2 E ~Z 4 Increased probability of forbidden transitions S 0 Competition of e-e correlation and relativistic effects He-like ions are the simplest for the two-photon decay measurements. Change of atomic structure with Z - - influences the two-photon decay rates Spectral shape of two photon emission allows test the whole atomic system - probe of relativistic effects in the strong central field in heavy atomic system 05-Feb-08 EAS, Riezlern 5

6 Introduction and motivation Theoretical spectral shape of the 2E transition Normalized intensity FWHM (Z=28) He-like Ni (Z=50) He-like U (Z=2) He Relative photon energy (E x /E 0 ) Full width at the half maximum of the two-photon energy distribution of the 2 S 0 state as function of Z Derevianko and Johnson, Phys. Rev. A 56 (997) Feb-08 EAS, Riezlern 6

7 05-Feb-08 EAS, Riezlern 7 Introduction and motivation Conventional technique for measuring the energy distribution of the two-photon decay: x-x coincidence Geometry He-like Au H.W. Schäffer et al. Phys. Lett. A 260 (999) 489 X-X coincidence spectrum FWHM Kr Ge Ni Atomic number (Z) Au He-like Au (Exp.)

8 05-Feb-08 EAS, Riezlern 8 ()()(Introduction and motivation Production of excited states by ionization (gas jet target) S electron /2 Probability for simultaneous ionization and excitation pionexcnljbp ionbexcnljpbz p S /2 Zt )ion exc ion exc b σ nlj ( b) = p ( b) 2π b db 2s /2 2p /2 2S /2 2s /2 2p 3/2 The ionization and/or excitation probabilities as a function of impact parameter 'b' (λ-compton wavelength) D.C. Ionescu and Th. Stöhlker, Phys. Rev. A 68 (2003) s /2 + 2s /2 2p /2 s /2 + 2s /2 2p 3/2 s /2 ionization U 89+ N 2

9 05-Feb-08 EAS, Riezlern 9 Introduction and motivation Production of the excited state in He-like ions by selective K-shell ionization of Li-like ions Li-like ion Ionization (Excited He-like ion) Decay (He-like ion) L shell 2s /2 K shell s /2

10 Data analysis and results Typical x-ray spectra of 300 MeV/u He-like Sn Sn N 2 Sn q+ Escape peak Total x-ray Yield Kα Kβ Projectile: Sn 47+ ; 300 MeV/u Target : N 2 Angle: 35 0 Particle Counter (MWPC) Dipole Magnet e - e - e E Energy, kev Sn N 2 Sn 48+ Escape peak M Energy, kev Gas Jet Coincidence registration of x-rays and up charged (He-like) ions 05-Feb-08 EAS, Riezlern 0 e - Stored Ions X-ray detectors Coincidence

11 Data analysis and results Typical x-ray spectra of 300 MeV/u He-like Sn Sn N 2 Sn q E Escape peak Escape peak Total x-ray Yield Kα Energy, kev Sn N 2 Sn 48+ M Kβ Energy, kev Energy (kev) Decay scheme of the excited states of He-like Sn He-like tin (Sn 48+ ) kev E EM 2.2(5) kev 05-Feb-08 EAS, Riezlern 2 S S M.74() 2E 2.5() kev S 0 E Coincidence registration of x-rays and up charged (He-like) ions 5.08(5) kev M2.38(2) kev.366(9) 2 P 2 3 P P P kev

12 Data analysis and results Typical x-ray spectra of 300 MeV/u He-like Sn Sn N 2 Sn Total x-ray Yield Escape peak Kα Kβ x Kα + M E Energy, kev Sn N 2 Sn 48+ Escape peak M M Energy (kev), projectile frame Energy, kev 05-Feb-08 EAS, Riezlern 2

13 05-Feb-08 EAS, Riezlern 3 Data analysis and results Theoretical 2E energy distribution from He-like ions Normalized intensity He He-like Ni He-like Sn He-like Nd He-like Yb He-like Hg He-like U Relative photon energy (E x /E 0 ) Normalized intensity He He-like Ni 0.4 He-like Sn 0.3 He-like Nd 0.2 He-like Yb He-like Hg 0. He-like U Relative photon energy (E x /E 0 ) Fully relativistic calculations of the two-photon energy distribution for He-like ions A. Volotka (Private communication)

14 Normalized intensity FWHM (Z=28) He-like Ni (Z=50) He-like U (Z=2) He Relative photon energy (E x /E 0 ) Theoretical efficiency curve of Ge detector E Escape peak M Energy, kev 05-Feb-08 EAS, Riezlern 4

15 Data analysis and results 05-Feb-08 EAS, Riezlern 5 Data analysis and comparision with theory Exp (Sn 48+ ) Z=50 Detector responce Z=92 Detector responce Relative photon energy (E x /E 0 ) Normalized intensity counts Z He He-like Ni He-like Sn He-like Nd He-like Yb He-like Hg He-like U Relative photon energy (E x /E 0 ) M resp. ratio (resol. 348keV) [x=( )/ x=( )] Exp. Theory ± Energy, kev (Lab)

16 Data analysis and results 05-Feb-08 EAS, Riezlern 6 Comparison of measured and theoretical 2E Spectral shape Exp-Theory/Theory U U Hg Yb Yb Sn Nd Ar Sn Ni Ar Escape peak region Normalized intensity He He-like Ni 0.4 He-like Sn 0.3 He-like Nd 0.2 He-like Yb He-like Hg 0. He-like U Relative photon energy (E x /E 0 ) -0. Exp (Sn 48+ ) Relative photon energy (E x /E 0 o ) "Experiment-theory/theory" ratio for He-like Ar, Sn, Yb and U theoretical values as a function of relative photon energy. Bin size : 20 channels ( kev) The spectral shape of 2E photons of He-like Sn has been discriminated from other He-like ions Relative photon energy (E x /E 0 )

17 05-Feb-08 EAS, Riezlern 7 Summary New approach is introduced for measuring the spectral distribution of 2E decay The spectral shape of 2E photons of He-like Sn are in agreement with the relativistic calculations The experimental results confirm, for the first time, predictions of relativistic theories.

18 05-Feb-08 EAS, Riezlern 8 Summary An experimental study of the production of the low-lying excited states in Helike high- and middle-z ions followed by the K-shell ionization of initially Li-like species has been performed: A technique for background-free two-photon transition measurements has been developed. Exclusive production of excited states in He-like ions New approach for investigation of exotic 2E decays The spectral shape of 2E photons of He-like Sn has been discriminated from other He-like ions. The experimental results confirm, for the first time, predictions of relativistic theories.

19 Many thanks for your attention 05-Feb-08 EAS, Riezlern 9