Angular Distribution Studies of the Time-Reversed Photoionization Process for decelerated high-Z ions

Th. Stöhlkera,b), X. Mab,c), T. Ludziejewskib), F. Boschb), O. Brinzanescub), H.F. Beyerb), J. Eichlerd), S. Hagmanne), C. Kozhuharovb), A. Krämera,b), D. Liesenb), P.H. Moklerb), H. Reichb), P. Rymuzaf), Z. Stachurag), P. Swiath), A. Warczakh)

a)IKF University of Frankfurt (Germany), b)GSI-Darmstadt (Germany), c)IMP, Lanzhou(China), d)HMI, Berlin(Germany), e)KSU-Manhatten (USA), f)INS Swierk (Poland), g)INP Krakow (Poland), h)University of Krakow (Poland)

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ATOMIC PHYSICS DIVISION
 

The photoionization is one of the most important interaction processes between radiation and matter. Recently, it has been proposed that the study of its time reversed analog which occurs in ion-atom collisions, i.e. Radiative Electron Capture (REC), can be applied for the investigation of the atomic photo effect in the domain of high-Z ions [1,2,3]. Some peculiarities of this technique are:

  • Photoionization can be studied for the ground and the excited states of highly charged and even bare high-Z ions
  • No corrections due to multiple scattering occurring in solid targets are required, leading in conventional photoionization studies for high-Z elements to a considerable broadening of the electron emission angle.
  • It can be studied at almost arbitrary collision energies, even close to the threshold and does not rely on the feasibility of suitable g-sources.
  • Due to the inverse kinematics of the REC process, differential cross sections at large backward angles can easily be measured.
  

Time-Reversal

Relativistic kinematics
Time Reversal Relativistic kinematics Relativistic kinematics

Experiment at the ESR Storage Ring

X-Ray Detection Environment

  

Supersonic jet

  

The ESR Storage Ring
x-ray detection
x-ray detection		 arrow supersonic jet arrow ESR

Results for K-REC

deviation from sin square

Deviations from the sin2θ distribution.
Solid triangles: 88 MeV/u U92+→N2;
open triangles: 310 MeV/u U92+→N2;
dashed and solid line: corresponding relativistic predictions

 polar representation

Polar representation of the K-REC angular distributions (projectile frame, solid circles) measured at 88 MeV/u and 310 MeV/u as a function of the emission angle

Decelerated Ions

High Energies
decelerated ions

Beam energy: 88 Mev/u

photoelectron energy 48 keV

 high energies

Beam energy: 310 Mev/u

photoelectron energy 170 keV
decelerated ions decelerated ions high energies high energies
 

Summary
We introduced the deceleration technique for angular-distributions studies of radiative electron capture into the bare uranium ions, i.e. at energies far below the energy required for the production of such high projectile charges. This allowed us to obtain for the first time differential data for photoionization of a high-Z hydrogenlike element in the low-energy regime. Our results clearly point out, that for high-Z elements retardation effects and magnetic corrections are still of importance even at low and intermediate energies. The comparison between our current data and the results obtained in a former experiment at the higher energy of 310 MeV/u is of particular importance. It allows us to distinguish between relativistic wave function effects and dynamically induced corrections. For the latter, the observed spin-flip transitions turn out to be most sensitive.

 
  References
  1. Th. Stöhlker et al., Comments At. Mol. Phys. 33, 271 (1997)
  2. A. Ichihara, T. Shirai, and J. Eichler, Phys. Rev. A. 54, 4954 (1996)
  3. Th. Stöhlker et al., Phys. Rev. Lett. 79, 3270 (1997)
  4. J. Eichler, A. Ichihara, and T. Shirai, Phys. Rev. A 51, 3017 (1995)
  5. Th. Stöhlker et al., Phys. Rev. Lett. 82, 3232 (1999)
  6. Th. Stöhlker et al., Phys. Rev. Lett. 86, 983 (2001)
  

for further information, please contact Thomas Stölker

Kai Lindenberg