Studies of the photoelectric effect at high energy

Blakeway, S J; Gelletly, W.; Faust, H.; Schreckenbach, K.

doi:10.1088/0022-3700/16/20/012

Cited by 4 publications

(2 citation statements)

References 13 publications

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“…4 refers to the electron angular distribution for photoionization of hydrogenlike uranium at the corresponding photon energy of 272 keV. We note that contrary to conventional photoionization studies for high-Z elements where scattering inside the solid targets leads to a considerable broadening of the photoelectron emission angle [20], no such effects have to be considered here. Moreover, compared to direct photoionizaton experiments the observed spin-flip transitions are found at a lower energy because in our experiment this effect appears to be enhanced by the Lorentz transformation.…”

Section: (Received 28 October 1998)mentioning

confidence: 99%

Angular Distribution Studies for the Time-Reversed Photoionization Process in Hydrogenlike Uranium: The Identification of Spin-Flip Transitions

Stöhlker

Ludziejewski²,

Bosch³

et al. 1999

Phys. Rev. Lett.

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The K-shell photoelectric effect for a hydrogenlike U 911 ion is studied by its time-reversed process occurring in relativistic collisions between bare uranium ions and low-Z target atoms. In the timereversed situation, an electron is captured into the 1s ground state with the simultaneous emission of a photon. We present an angular differential study of these transitions for laboratory observation angles between nearly 0 ± and 150 ± . Our observation of photon emission close to 0 ± allowed us to identify spin-flip contributions to the photoionization process and to determine their relative strength.[S0031-9007 (99)08948-6] PACS numbers: 34.70. + e, 12.20.DsPhotoionization is one of the most important interaction processes between radiation and matter [1,2]. We have previously shown that for high-Z ions photoionization is studied best via its inverse reaction, radiative electron capture (REC) [3][4][5] in energetic ion-atom collisions [6]. For very high-Z systems, relativistic effects become important and require an exact theoretical treatment [1,7,8] adopting relativistic electron wave functions and including retardation, i.e., all multipole orders of the photon field [9]. For the quantitative assessment of relativistic effects in high-Z ions, angular distributions are a very sensitive probe [10]. This has already been shown for direct photoionization of neutral atoms at high energies (.500 keV), where retardation leads to a strong forward peaking of the photoelectron angular distribution and where spin-flip effects were observed close to 0 ± (see, e.g., [11]). The inverse reaction for a pure hydrogenlike system lends itself to a different critical test, namely, measuring the deviation from a sin 2 u distribution. For REC into the K shell of bare nonrelativistic ions, this reference distribution comes about by the cancellation between the effects of retardation, on the one hand, and the Lorentz transformation into the laboratory system, on the other hand [12,13]. Similar cancellations for various atomic processes are known to occur also in relativistic systems [14]. For high enough charges and energies, however, these cancellations are no longer complete. In particular, for Z 92 and for REC into the K shell, a significant cross section at forward angles has been predicted and shown to be a unique signature of spin-flip transitions [4,8,15].In this Letter, we report the first experimental study of a complete photon angular distribution for radiative electron capture into the K shell of a bare high-Z ion (uranium, Z 92). Our measurements encompass laboratory observation angles from near 0 ± to 150 ± , permitting the identification of spin-flip contributions that lead to photon emission at 0 ± . Photon emission at 0 ± and at 180 ± is forbidden by angular momentum conservation unless a magnetic spin-flip transition accounts for the spin of the emitted photon [15]. Furthermore, we deduce the electron angular distribution following photoionization of hydrogenlike uranium, i.e., for an explicitly point Coulombic high-Z...

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Section: (Received 28 October 1998)mentioning

confidence: 99%

Angular Distribution Studies for the Time-Reversed Photoionization Process in Hydrogenlike Uranium: The Identification of Spin-Flip Transitions

Stöhlker

Ludziejewski²,

Bosch³

et al. 1999

Phys. Rev. Lett.

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“…Most importantly, no corrections due to photoelectron scattering occurring in solid targets are required. In conventional photoionization studies for high-Z elements, these effects lead to a considerable loss in the definition of an electron emission angle [7], in particular, at lower photon energies. Therefore, in the high-Z regime, almost none of the few fine structure-and angle-resolved photoionization data can be compared with theory [6].…”

mentioning

confidence: 99%

Near-Threshold Photoionization of Hydrogenlike Uranium Studied in Ion-Atom Collisions via the Time-Reversed Process

Stöhlker

Ludziejewski

et al. 2001

Phys. Rev. Lett.

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Radiative electron capture, the time-reversed photoionization process occurring in ion-atom collisions, provides presently the only access to photoionization studies for very highly charged ions. By applying the deceleration mode of the ESR storage ring, we studied this process in low-energy collisions of bare uranium ions with low- Z target atoms. This technique allows us to extend the current information about photoionization to much lower energies than those accessible for neutral heavy elements in the direct reaction channel. The results prove that for high- Z systems, higher-order multipole contributions and magnetic corrections persist even at energies close to the threshold.

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Photon-produced electron fluence calculated with photoelectron angular distribution of Sauter expression

Nariyama

2006

Radiation Physics and Chemistry

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Studies of the photoelectric effect at high energy

Cited by 4 publications

References 13 publications

Angular Distribution Studies for the Time-Reversed Photoionization Process in Hydrogenlike Uranium: The Identification of Spin-Flip Transitions

Angular Distribution Studies for the Time-Reversed Photoionization Process in Hydrogenlike Uranium: The Identification of Spin-Flip Transitions

Near-Threshold Photoionization of Hydrogenlike Uranium Studied in Ion-Atom Collisions via the Time-Reversed Process

Photon-produced electron fluence calculated with photoelectron angular distribution of Sauter expression

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