[3dem] reflections from gold fiducials

[Schmid, Michael F.]

We have seen these before; they are a nuisance. Sometimes they weaken the image of the gold fiducial or otherwise confuse the tracking. Crystalline ice chunks do this too, of course, usually much worse.

On 11/6/17, 1:13 PM, "3dem on behalf of Lars-Anders Carlson" <3dem-bounces at ncmir.ucsd.edu on behalf of lars-anders.carlson at umu.se> wrote:

    Dear community,
    We encountered something during tilt series acquisition recently that I 
    hadn't seen before: several 10 nm gold fiducials gave clear reflections, 
    see attached image (compressed snapshot - it looks stronger in the 
    original images).
    
    The reflections were often symmetrically arranged around a fiducial and 
    would then disappear at the next tilt ange. We used a 100 um objective 
    aperture at a Krios at 300kV. Admittedly I never worried about the 
    crystalline arrangement of gold fiducials before, so I took some higher 
    mag images of the fiducials, and some of them look mosaic, others more 
    monocrystalline (see image), which could explain why some cause more 
    reflections than others.
    
    Is this something people have encountered before? Are some batches of 
    fiducials better ordered than others at the atomic level? I'm curious to 
    hear what people think of this since it fascinated me...
    
    Cheers,
    Lars
    
    -- 
    Lars-Anders Carlson
    Assistant Professor
    Dept of Medical Biochemistry and Biophysics
    Wallenberg Centre for Molecular Medicine
    Umeå University
    901 87 Umeå, Sweden
    
    lab website including OPEN POSITIONS:
    http://www.carlsonlab.se/