Dear Tarek
There are several things to consider: 1-At an MX beamline the X-ray fluorescence (XRF) scans are usually used to define good energies for measurement of anomalous data. While XANES and XRF in general are similar techniques, they are used for very different applications. This said, it would in principal be possible to do these experiments at an MX beamline. However, in real-life the resolution of both the monochromator and the detector(s) will most likely not be sufficient to obtain high-resolution XANES data. Also, XANES usually employs evacuated endstations, a feature rarely seen at MX beamlines. Another factor is the uncalibrated detectors. In MX we usually take raw counts as an arbitrary signal for the scans. In Xanes you are interested in absolute values calibrated towards the incident photon flux (I0). 2-f'' is in fact directly proportional to the measured signal, but it is not exactly a fit. It's relation to f' is defined by the Kramers-Kronig relation: http://skuld.bmsc.washington.edu/scatter/AS_kk.html 3-as mentioned before, the data most likely will not be of high enough quality for these estimations. Also you would have to measure reference data of defined oxidation states at the exact same setup. If you are interested in these kinds of experiments you should preferably apply for beamtime at an dedicated instrument, preferably at a synchrotron where you can also use an MX beamline. Best, Florian __________________________________________ Paul Scherrer Institut Florian Dworkowski Beamline Scientist X10SA WSLA/219 CH-5232 Villigen PSI Telefon: +41 56 310 35 84 E-Mail: florian.dworkow...@psi.ch From: Tarek DawoD [mailto:tkda...@yahoo.com] Sent: Dienstag, 22. Juli 2014 22:40 Subject: Off-Topic Q / X Ray FLuoresence Scan Vs XANES Doing Fluroscence scan for protein crystal at Cu wavelength prior MAD or SAD experiment shows usually fig like this https://www.dropbox.com/s/800463dlcmws6d4/fig.png 1- Fig A should represent X ray fluorescence scan. is it the same as X ray absorption scan. what does count represent in fig A (is it equal to the intensity of the emission). 2- i am wondering whether F double prime in Fig B is just a fit for counts in Fig A, it looks the same. could F" or counts be converted to I/I0 or F/I0 to replot the data against these value as in XANES. in other word, Is X ray fluorescence scan in fig A the same as X-ray absorption near-edge structure (XANES)? could XANES be collected at the same beamline where diffraction data are collected for crystal ? 3- could data from Fluorescence scan in Fig A or B used to determine the oxidation or coordination number for the metal say copper for example in protein? thank YOU regards T. DawoD
