Here’s a fun looking picture that showed up during one of my analysis routines.



I’d been averaging images together from some rather weak scattering images to improve the statistics when one of the results produced a rather unusual image. What we “should” be seeing is a single peak/feature in the center, but instead there are 8-9 weak peaks over the area in a uniform spacing. Now, the first thing I thought of when seeing this (indeed the first thing any x-ray person I’ve shown this to thinks) is, “what d-spacing does this diffraction pattern correspond to and what’s causing it.” We’re looking at x-ray scattering data, we normally see diffraction conditions satisfied during our work, and it would fit perfectly with what we’re seeing here. Except that it doesn’t.

This is a classic example of seeing what you want to see. The length scales are all wrong and the intensity doesn’t match, something else must be going on here.

It turns out I had mislabeled one of the scan numbers in my analysis and so the program blindly added together images from different sets where the detector was in a different position each time. The detector (and sample) was moved systematically between each of these and so we end up with a regular array of spots in the final image once everything is added together.

The picture looks nice though, and looks at first glance to be exactly something it isn’t.

Not much to say here, just that we’ve managed to get speckled scattering patterns from a surface monolayer of gold atoms.



The speckle is not very well developed, the contrast isn’t great. But it’s clearly there and very static at room temperature.