A new 2D-ACAR apparatus has been developed. A pair of compact position-sensitive γ-ray detectors are used, each of which consist of 2.2 × 2.2 × 15 mm3 BGO scintillator blocks bunched into a 25 × 21 array with 2.4 mm pich, and coupled to a position-sensitive photomultiplier tube. The new apparatus has been applied to study the wave functions of the delocalized positronium(Ps) in alkali halides and the localized Ps in complex salt [Zn(ptz)6](BF4)2. It has been observed that all the Bloch Ps satellite peaks in KCl and KI, except for the  peaks, are extremely weak. The anisotropies of the Ps wave function in [Zn(ptz)6](BF4)2 changes near the temperature where the Fe analogue of the complex salt exibits spin-crossover transition.
|Number of pages||3|
|Journal||Materials Science Forum|
|Publication status||Published - 1997|
- Alkali Halide
- Complex Salt
- Position Sensitive Detector