[Ifeffit] Fluorescence sample thickness

I'm preparing for an XAS measurement in fluorescence of a solution-phase sample that will be measured in a capillary tube. I anticipate being able to control the concentration fairly easily, and I'm trying to figure out what the best capillary diameter would be. Is there a good way to figure this out? Rachel Wallick Chemistry Graduate Student Van der Veen Group University of Illinois at Urbana-Champaign 3011 Materials Research Laboratory