ISSN:
1432-0630
Keywords:
Positron lifetimes
;
Liquid crystals
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
Abstract Positron lifetimes have been measured as a function of temperature in 4-butyloxybenzal-4′-ethylaniline (BEA). BEA has been previously reported to have two liquidcrystalline phases (smectic and nematic) with transition temperatures as follows: solid → smectic, 40.5° C; smectic → nematic, 51.0° C; and nematic → isotropic liquid, 65.5° C. Positron life time spectra were resolved into two components, with the shorter component τ1 remaining approximately constant in all phases, and τ2 exhibiting reversible changes at all of the above transitions. In addition, an irreversible discontinuity in the τ2 lifetime was observed in the vicinity of 28° C, indicating the presence of a new phase (phase X) of BEA. The τ2 andI 2 values obtained for the various phases of BEA are: solid (1.25 nsec, 7.1%), phase X (1.97 nsec, 26.2%), smectic (2.36 nsec, 23.6%), nematic (2.72 nsec, 28.3%), and isotropic liquid (2.69 nsec, 29.8%).
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00884414
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