Dec 30, 2015
The New X-Ray Guy
1. Frankenthal / Mannheim
2. La Chapelle Aux Bois
3. Kasierslautern
4. Göttingen
Peter Müller Peter Mueller
• Judging the Quality of a Crystal.
• Determining the Best Exposure Time.
• Data Collection Strategy.
And now: Some Crystallography
The Rocking Curve
Judging the Quality of the X-tal
Analyze Rocking
Number of frames in both directions
Size of the boxhalfwidth =mosaicity
Compare two (or more) immages that differ only in exposure time.
Does a longer exposure time add information to the immage?
Determining the Exposure Time
File Display 10 second frame
File Display 20 second frame
Analyze ContrastFile
Display30 second frame
Analyze Contrast
Determining the Exposure Time
20 seconds is better than 10 seconds.
30 seconds not better than 20 sconds.
Our exposure time is20 seconds per frame.
Always collect a new dark current at your exposure time or at least load an older (but not too old!) dark current taken at your exposure time.
compare
Collect Dark Current
Detector Dark Current
Now you are ready for data collection
What is the best strategy?
phi- and omega-scans
Incident beam
Detector
Diffracted beamhkl reflection
Reciprocal lattice
hkl lattice planes
Crystal
hkl reciprocal lattice point
s
s
Q CO
P
d
Ewald sphere with radius r = 1/
Phi-scansat different omega-angles
Omega-scansat different phi-angles
phi- and omega-scansare orthogonal
...try to combine them!
Collect Dark Current
Edit Multi Run
Three 200° omega-scansand two 360° phi-scans
Two 200° omega-scansand one 360° phi-scan
that‘s plenty forany situation.
is enough for mmm and higher.