Studies of electron correlation in the photoionization process

Thesis/Dissertation · Thu Mar 01 00:00:00 EST 1979

DOI:https://doi.org/10.2172/1022112· OSTI ID:1022112

Rosenberg, Richard Allen ^[1]

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1. Univ. of California, Berkeley, CA (United States)

Electron correlation is a result of the interaction of two or more electrons confined in a region of space, and may conveniently be treated under the formalism of configuration interaction (CI). Photoionization provides a rather direct experimental method for studying configuration interaction. The types of CI involved in the photoionization process can be divided into three categories: initial state configuration interaction (ISCI), final ionic state configuration interaction (FISCI), and continuum state configuration interaction (CSCI). This thesis deals with experimental studies which reveal how the various types of CI may become manifested in photoionization. The experimental methods utilized in this work are photoelectron spectroscopy (PES), electron impact spectroscopy (EIS), and time-resolved fluorescence spectroscopy. The EIS was carried out following the discovery that the UV lamp on a Perkin-Elmer photoelectron spectrometer could be utilized as a source of low energy electrons. The time-resolved fluorescence work utilized both the tunability and the time structure of the radiation available at the Stanford Synchrotron Radiation Laboratory (SSRL). A commercial photoelectron spectrometer equipped with a conventional UV lamp (Hei, Nei) was employed for some of the PES studies, and a novel time-of-flight photoelectron spectrometer was developed for the PES work performed using synchrotron radiation. The PES of Ba, Sm, Eu, and Yb was studied using both Hei (22.22 eV) and Nei (16.85 eV) radiation. Satellite structure observed in these spectra using Nei (and for Yb, Hei also) radiation could be satisfactorily explained by ISCI alone. The Hei spectra of Sm, Eu, and, in particular, Ba showed dramatic changes in the satellite population which could only be explained by a new mechanism, autoionization, which is a special form of CSCI. The detailed nature of this mechanism was explored in Ba using synchrotron radiation. It was found that the autoionizing level decays preferentially via an Auger type mechanism. Further insight into autoionization was gained in the electron impact/ejected electron spectra of Ba (5p⁶ 6s²) and Yb (5p⁶ 4f¹⁴ 6s²). It was found that autoionizing levels excited above the first (5p)^-1 threshold decay primarily in a two-step Auger process, leading to a relatively large number of doubly charged ions. For autoionizing states below the (5p)^-1 limit, decay appears to go to ground and excited states of the singly charged ion. The first experimental determination of the lifetime of the XeII 5s5p^{6 2}S_1/2 state yielded a value of 34.4(6) nsec. Reasonable agreement with theory could only be reached by including both FISCI and relativistic effects in calculating the lifetime.

• Research Organization: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC02-05CH11231
• OSTI ID: 1022112
• Report Number(s): LBL-8948; TRN: US201118%%313
• Resource Relation: Related Information: Designation of Academic Dissertation: Doctoral; Academic Degree: Ph.D.; Name of Academic Institution: University of California Berkeley
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
AUTOIONIZATION
CONFIGURATION INTERACTION
DECAY
ELECTRON CORRELATION
ELECTRON SPECTRA
ELECTRONS
EXCITED STATES
FLUORESCENCE
FLUORESCENCE SPECTROSCOPY
LIFETIME
LIGHT BULBS
PHOTOELECTRON SPECTROSCOPY
PHOTOIONIZATION
RADIATIONS
SATELLITES
SPECTRA
SPECTROMETERS
SPECTROSCOPY
SYNCHROTRON RADIATION