Re: [Ifeffit] Help in background removal with Athena
Hi Irina, I guess in a normal situation you would want to FT at least 5 k(1/A) range to get some sort of shape to your FT peaks which would normally be a range of about 2 -7 k so maybe 190 eV above the edge. However added to that the data has to be good, I am not a C XAS expert but looking at your data I am unsure that all the oscillations are due the x-rays scattering , some might be experimental artefact which would then make the analysis even less trustworthy. WRT your data after the signal begins to die about 400 eV, i.e. you have ca 110 eV of data I might trust on a good day and even then I'd be more reassured if these were several scans added rather than just one. (I can't tell if this is the case). I doubt there is useful stuff that can be extracted past that point. Hence I think all that is probably there is the pre-edge changes in the XANES which I presume you are looking at as well. Thanks Fred -- This e-mail and any attachments may contain confidential, copyright and or privileged material, and are for the use of the intended addressee only. If you are not the intended addressee or an authorised recipient of the addressee please notify us of receipt by returning the e-mail and do not use, copy, retain, distribute or disclose the information in or attached to the e-mail. Any opinions expressed within this e-mail are those of the individual and not necessarily of Diamond Light Source Ltd. Diamond Light Source Ltd. cannot guarantee that this e-mail or any attachments are free from viruses and we cannot accept liability for any damage which you may sustain as a result of software viruses which may be transmitted in or with the message. Diamond Light Source Limited (company no. 4375679). Registered in England and Wales with its registered office at Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, United Kingdom
To add to Fred's comments, as someone who has done a lot of soft x-ray spectroscopy, there is simply not enough "room" above the edge to do EXAFS at these energies. There is a lot of competition from molecular resonances and other light elements. For instance, the feature around 290 eV is due to a 1s --> sigma^* transition. Also, the feature at ~400 eV could as likely originate from some spurious nitrogen in your system than photoelectron scattering. Carbon NEXAFS is well established to look at the bonding and chemistry of SAMs, graphene, diamond, etc. I suggest you search that out. Jo Stohr has a good book on the subject (http://www-ssrl.slac.stanford.edu/stohr/). Also, I would highly recommend getting better quality data. Even with SLG you should be able to count for an appreciable time to get higher quality data. This will reveal a lot of the resonances you see in carbon, and will allow your angle dependent measurements to be more quantifiable. (I assume you are doing angle dependence to probe the orientation of the graphene on whatever substrate you have). Best regards, Rob Meulenberg -- Robert W. Meulenberg Associate Professor of Physics Laboratory for Surface Science and Technology Department of Physics and Astronomy University of Maine Orono, ME 04469 phone: 207-581-2245 email: robert.meulenberg@maine.edu
participants (2)
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fred.mosselmans@diamond.ac.uk
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Robert Meulenberg