Doppler broadened peks

[Jean-Charles ABBE <abbe@in2p3.fr>]

Another well know example of doppler broadened peak is the annihilation
peak at 511 keV which is generally twice as broad, and not constant
depending on the sample, as the width of a neighbour ray. This is due to
moving positronium annihilation, not at rest, which results in a momentum
with a longitunal component towards or opposite to the detector. Exactly
the same problem with a recoiling atom, provided the lifetime is long
enough.
This doppler broadened annihilitaion line can serve as an interesting basis
for experimental work with students but it is also largely used in research
to derive information on the nature of the sample.One then measures the
variations of the broadness of the line with the nature, the temperature,
the pressure, ... of the sample. This momentum distribution is similarly
derived through measurement of the angular distribution between the two
annilation rays (no longer colinear but slightly shifted).

***********************************
Jean-Charles ABBE
Laboratoire SUBATECH
Faculte des Sciences et Techniques
Departement de Physique
2, Rue de la Houssinière
BP 92208
44 322 NANTES CEDEX 3

Tel 33 (0)2 51 12 55 10
Fax 33 (0)2 51 85 84 79

ABBE@SUBATECH.IN2P3.FR


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