A critical assessment of the QEXAFS method (abstract) Available to Purchase

The idea of recording an x‐ray‐absorption spectrum ‘‘on the fly’’ when a mechanically stable monochromator is being slewed smoothly and continuously over a given energy range has been proposed and successfully demonstrated in 1988 [R. Frahm, HASYLAB Annual Report (unpublished), 1987, p. 374; Nucl. Instrum. Methods A 270, 578 (1988)]. This procedure constitutes what is now known as the QEXAFS method. The question ‘‘How quick is QEXAFS?’’ has been examined in some detail at the Kobe conference [R. Frahm and Joe Wong, Jpn. J. Appl. Phys. 32, 188 (1993)]. Thus the QEXAFS technique provides a novel characterization tool to study the bonding and local atomic structure in materials with a time resolution of the order of seconds. In the present paper, a critical assessment of this technique is provided in terms of spectral quality and resolution as a function of various QEXAFS experimental parameters such as scan rate, integration time, type of monochromator used, as well as an experimentally definiable energy window over which a QEXAFS data point is collected. Model compounds with well defined shape preedge XANES and white line features and long k‐range EXAFS are used as test systems to arrive at a set of practical experimental parameters. The versatility, application, and limitations of this time‐resolved spectroscopic tool will be discussed.