a.kumar@gsistoe_exp/presentations/talks/PDF_files/...05-Feb-08 EAS, Riezlern 1 Spectral shape of two-photon decay from 2S state in He-like tin Ajay Kumar GSI, Darmstadt [email protected]

05-Feb-08 EAS, Riezlern 1

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

Ajay KumarGSI, [email protected]

Team

S. Trotsenko1,2, D. Banas3, H. Beyer1, H. Bräuning1, A. Gumberidze1, S. Hagmann1,2, S. Hess1,2, P. Jagodziński3, C. Kozhuharov1, R. Reuschl1,2,S. Salem1, U. Spillmann1,2 , M. Trassinelli1,4, A. Volotka5, G. Weber1,6, Th. Stöhlker1,6 and the ESR-Team

1Atomic Physics Group, GSI-Darmstadt, Germany2IKF, University of Frankfurt, Germany3Institute of Physics, Swietokrzyska Academy, Kielce, Poland4Institut des NanoSciences de Paris, Campus Boucicaut, 75015 Paris, France5Institut für Theoretische Physik, TU Dresden, Germany 6Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Germany


OutlineOutline

Introduction and motivation

Experimental details

Data analysis and results

Summary


TwoTwo--photon decay in Hephoton decay in He--like ionslike ions

Maria Göppert-MayerNobel Laureate, 1963

1s2s 1S0

1s2 1S0

E1+ E2 = E0 = Ei- Ef

He-isosequence

1s2s 1S0 → 1s2 1S0 + E1+ E2

Single photon transition

E0

E2

E1 1s2s 1S0 → 1s2 1S0 + E0

Two-photon (2E1) decayor

One-electron two-photon decay

is forbidden 00 =→= JJ

M. Göppert, Naturwissenschaften 17 (1929) 932M. Göppert-Mayer, Ann, Phys. 9 (1931) 273

0.0 0.2 0.4 0.6 0.8 1.00

1

2

3

Nor

mal

ized

inte

nsity

Ex / E0

Z=92He-like ion

Calculated photon energy distribution of 2 1S0 → 1 1S0transition

Derevianko and Johnson, Phys. Rev. A 56 (1997) 1288


Ex=E1/E0=E2/E0


Energy differential emission rate of two-photon decay

1

2

11 21)( dEMEEdEEA fi∝ ∑ ⎥⎦

⎤⎢⎣

⎡+

>><<+

+>><<

=2

12

1

21

EEiDnnDf

EEiDnnDf

Mnini

fi

10

22

0

11 1; f

EEf

EEf −===

1

2

1111 )1()( dEMffdEEA fi−∝

Overall shape of the spectral distribution

0.0 0.2 0.4 0.6 0.8 1.00.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Nor

mal

ized

inte

nsity

Photon energy fraction0.0 0.2 0.4 0.6 0.8 1.0

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Nor

mal

ized

inte

nsity

Photon energy fraction

Total emission rates

∫= ifE

T dEEAA0 11)(

21


Increased probability of forbidden transitions

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

WhyWhy goinggoing to to highlyhighly chargedcharged highhigh--ZZ ionsions ??IntroductionIntroduction and and motivationmotivation

1 1S0

2 1S0

2 3S12 3P1

2 3P0

2 3P2

2 1P1

E1M1E1

2E1M1

E1

~Z10~Z6

~Z4~Z12


Full width at the half maximum of the two-photon energy distribution of the 2 1S0 state as function of ZDerevianko and Johnson, Phys. Rev. A 56 (1997) 1288

Theoretical spectral shape of the 2E1 transitionTheoretical spectral shape of the 2E1 transitionIntroduction and motivation

0.0 0.2 0.4 0.6 0.8 1.00.00.10.20.30.40.50.60.70.80.91.0

(Z=28) He-like Ni (Z=50) He-like U (Z=2) He

Nor

mal

ized

inte

nsity

Relative photon energy (Ex/E0)

FWHM


ConventionalConventional techniquetechnique forfor measuringmeasuring thethe energyenergydistributiondistribution of of thethe twotwo--photonphoton decaydecay: : xx--x x coincidencecoincidence

X-X coincidence spectrumH.W. Schäffer et al. Phys. Lett. A 260 (1999) 489

Geometry He-like Au

IntroductionIntroduction and and motivationmotivation

0 20 40 60 80 1000.700.720.740.760.780.800.82

FWH

M

Atomic number (Z)

Ni AuGeKr

He-like Au(Exp.)


ProductionProduction of of excitedexcited statesstates byby ionizationionization (gas (gas jetjet targettarget))

Probability for simultaneous ionization and excitation

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) 022705

2s1/2 → 2p3/2

2s1/2 → 2p1/2

1s1/2 ionization1s1/2 +2s1/2 → 2p1/2

1s1/2 +2s1/2 → 2p3/2

U89+ → N2

ZZp

1S electron 1/2

1S 1/2

2S 1/2

tb

︶︵︶︵︶︵ bpbpbp excnlj

ionexcionnlj ≈

dbbbpb excionexcionnlj 2)()( πσ ∫=

IntroductionIntroduction and and motivationmotivation


ProductionProduction of of thethe excitedexcited statestate in in HeHe--likelike ionsions bybyselectiveselective KK--shellshell ionizationionization of of LiLi--likelike ionsions

K shell

LiLi--like ionlike ion Ionization Ionization (Excited He(Excited He--like ion)like ion)

Decay (HeDecay (He--like ion)like ion)

L shell

1s1/2

2s1/2



5 10 15 20 25 30 35

1000

10000

100000

Cou

nts

Total x-ray Yield

Energy, keV

Kα

Kβ

Esca

pe p

eak

5 10 15 20 25 30 35

10

100

1000

10000

Cou

nts

Energy, keV

Esca

pe p

eak

M1

2E1

Sn47++ N2 →Snq+

Sn47++ N2 →Sn48+

Coincidence registration of x-rays and up charged (He-like) ions

Particle Counter(MWPC)

Dipole Magnet

Gas Jet

e-

e-e-

e-

X-ray detectorsStored Ions

Coincidence

Projectile: Sn47+; 300 MeV/uTarget : N2Angle: 350


Typical x-ray spectra of 300 MeV/u He-like Sn



5 10 15 20 25 30 35

10

100

1000

10000

Cou

nts

Energy, keV

Esca

pe p

eak

M1

2E1

5 10 15 20 25 30 35

1000

10000

100000

Cou

nts

Total x-ray Yield

Energy, keV

Kα

Kβ

Esca

pe p

eak Decay scheme of the excited states of He-like Sn

Sn47++ N2 →Snq+

Sn47++ N2 →Sn48+

32

34

36

8.55

8.58

8.61

8.24

8.28

8.32

11S0

2E1

He-like tin (Sn48+)

25.637 keV

2.15(11)

25.712 keV 2.12(15)1.366(9)

23P023P1

21S0

23S1Ene

rgy

(keV

)M1

E1

E1E1M1

M2

1.74(11)

26.016 keV

5.08(15) 25.983 keV

1.38(12) 25.707 keV25.72 keV

21P123P2

Coincidence registration of x-rays and up charged (He-like) ions




5 10 15 20 25 30 35

1000

10000

100000

Cou

nts

Total x-ray Yield

Energy, keV

Kα

KβEs

cape

pea

k

5 10 15 20 25 30 35

10

100

1000

10000

Cou

nts

Energy, keV

Esca

pe p

eak

M1

2E1

Sn47++ N2 →Sn

Sn47++ N2 →Sn48+

4

8

12

41 42 43

2

4

6

x 103

Cou

nts

Energy (keV), projectile frame

M1


Kα + M1


Theoretical 2E1 energy distribution from HeTheoretical 2E1 energy distribution from He--like ionslike ions

0.0 0.2 0.4 0.6 0.8 1.00.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

He He-like Ni He-like Sn He-like Nd He-like Yb He-like Hg He-like U

Nor

mal

ized

inte

nsity


0.5 0.6 0.7 0.8 0.9 1.00.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0


Nor

mal

ized

inte

nsity


Fully relativistic calculations of the two-photon energy distribution for He-like ionsA. Volotka (Private communication)



Theoretical efficiency curve of Theoretical efficiency curve of GeGe detectordetector

0.0 0.2 0.4 0.6 0.8 1.00.00.10.20.30.40.50.60.70.80.91.0

(Z=28) He-like Ni (Z=50) He-like U (Z=2) He

Nor

mal

ized

inte

nsity


FWHM

5 10 15 20 25 30 35

10

100

1000

10000

Cou

nts

Energy, keV

Esca

pe p

eak

M1

2E1


0.5 0.6 0.7 0.8 0.9 1.0

1

10

100

1000

Exp (Sn48+) Detector responce

Cou

nts

Relative photon energy (Ex/E0)0.5 0.6 0.7 0.8 0.9 1.0

1

10

100

1000

Exp (Sn48+)

Cou

nts

Relative photon energy (Ex/E0)0.5 0.6 0.7 0.8 0.9 1.0

1

10

100

1000

Exp (Sn48+) Z=50 Z=92 Detector responce

Cou

nts


Data analysis and comparision with theory


0 5 10 15 20 25 30 35 40 450.01

0.1

1

10

100

1000

10000

M1 resp. (resol. 348keV)

coun

ts

Energy, keV (Lab)

0.0 0.2 0.4 0.6 0.8 1.00.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0


Nor

mal

ized

inte

nsity


Z Counts ratio [x=(0.80-0.92)/ x=(0.50-0.68)]

Exp. Theory

28 0.403

50 0.390±0.003 0.386

60 0.374

70 0.366

92 0.324


Comparison of measured and theoretical 2E1 Spectral shape

0.5 0.6 0.7 0.8 0.9-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

Escape peak region

U Yb Sn Ar

Exp-

Theo

ry/T

heor

y


0.5 0.6 0.7 0.8 0.9-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

Escape peak region

U Hg Yb Nd Sn Ni Ar

Exp

-The

ory/

Theo

ry

Relative photon energy (Ex/Eo)"Experiment-theory/theory" ratio for He-like Ar, Sn, Yband U theoretical values as a function of relative photon energy. Bin size : 120 channels (1 keV)


0.5 0.6 0.7 0.8 0.9 1.00.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0


Nor

mal

ized

inte

nsity


0.5 0.6 0.7 0.8 0.9 1.0

1

10

100

1000

Exp (Sn48+)

Cou

nts


The spectral shape of 2E1 photons of He-like Snhas been discriminated from other He-like ions


SummarySummary

New approach is introduced for measuring the spectral distribution of 2E1 decay

The spectral shape of 2E1 photons of He-like Sn are in agreement with the relativistic calculations

The experimental results confirm, for the first time, predictions of relativistic theories.


SummarySummary

An experimental study of the production of the low-lying excited states in He-like 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 2E1 decays

The spectral shape of 2E1 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.


Many thanks for your attentionMany thanks for your attention

Documents

a.kumar@gsistoe_exp/presentations/talks/PDF_files/...05-Feb-08 EAS, Riezlern 1 Spectral shape of two-photon decay from 2S state in He-like tin Ajay Kumar GSI, Darmstadt [email protected]