The New X-Ray Guy

1. Frankenthal / Mannheim

2. La Chapelle Aux Bois

3. Kasierslautern

4. Göttingen

Peter Müller Peter Mueller

The New X-Ray Guy

The New Cryostream

• Judging the Quality of a Crystal.

• Determining the Best Exposure Time.

• Data Collection Strategy.

And now: Some Crystallography

Initial Immages

Judging the Quality of the X-tal

Take two immages 90° appart.

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?

The Platform Geometry

omega

phi

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.

The Zero-Frames

The Zero-Frames

We have a new HOMEPAGE

http://web.mit.edu/x-ray

Next Meeting

Tuesday November 9,11:00 a.m.AMDUR room (here)

Data Reduction with SAINT and SADABS