THE SECONDARY EXTINCTION CORRECTION
It is shown that Darwin's formula for the secondary extinction correction, which has been universally accepted and extensively used, contains an appreciable error in the x-ray diffraction case. The correct formula is derived. As a first order correction for secondary extinction, Darwin showed that one should use an effective absorption coefficient mu + gQ where an unpolarized incident beam is presumed. The new derivation shows that the effective absorption coefficient is mu + 2gQ(1 + cos/sup 4/2 theta )/(1 plus or minus cos/sup 2/2 theta )/s up 2/, which gives mu + gQ at theta =0 deg and theta = 90 deg , but mu + 2gQ at theta = 45 deg . Darwin's theory remains valid when applied to neutron diffraction. (auth)
- Research Organization:
- Univ. of Chicago, IL (United States)
- Sponsoring Organization:
- Sponsor not identified
- NSA Number:
- NSA-17-032829
- OSTI ID:
- 4875506
- Report Number(s):
- CONF-64-2; AED-Conf-63-053-3
- Resource Relation:
- Conference: American Cyrstallographic Assn. Meeting, Cambridge, MA (United States), 28-30 Mar 1963
- Country of Publication:
- United States
- Language:
- English
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