Multiple bifurcations with signal enhancement in nonlinear mid-infrared thermal lens spectroscopy

The Analyst ◽  
2017 ◽  
Vol 142 (11) ◽  
pp. 1882-1890 ◽  
Author(s):  
Atcha Totachawattana ◽  
Mi K. Hong ◽  
Shyamsunder Erramilli ◽  
Michelle Y. Sander
Keyword(s):  
Phase Transitions ◽  
Liquid Crystals ◽  
Thermal Lens ◽  
Signal Enhancement ◽  
Photothermal Spectroscopy ◽  
Mid Infrared ◽  
Thermal Lens Spectroscopy ◽  
Multiple Phase

Mid-infrared nonlinear photothermal spectroscopy with multiple bifurcations is demonstrated on liquid crystals across multiple phase transitions.

Theory of amphiphilic liquid crystals: Multiple phase transitions in a model micellar system

1989 ◽  
Vol 91 (1) ◽  
pp. 528-538 ◽  
Author(s):  
Mark P. Taylor ◽  
Alan E. Berger ◽  
Judith Herzfeld
Keyword(s):  
Phase Transitions ◽  
Liquid Crystals ◽  
Micellar System ◽  
Multiple Phase

Multiple phase transitions investigated by high-speed TEM

1990 ◽  
Vol 48 (4) ◽  
pp. 550-551
Author(s):  
Oleg Bostanjoglo ◽  
Peter Thomsen-Schmidt
Keyword(s):  
Phase Transitions ◽  
High Speed ◽  
Short Exposure ◽  
Semiconductor Film ◽  
Time Resolved ◽  
Short Exposure Time ◽  
Multiple Phase ◽  
Model Substance ◽  
History Of ◽  
Electron Image

Thin GexTe1-x (x = 0.15-0.8) were studied as a model substance of a composite semiconductor film, in addition being of interest for optical storage material. Two complementary modes of time-resolved TEM were used to trace the phase transitions, induced by an attached Q-switched (50 ns FWHM) and frequency doubled (532 nm) Nd:YAG laser. The laser radiation was focused onto the specimen within the TEM to a 20 μm spot (FWHM). Discrete intermediate states were visualized by short-exposure time doubleframe imaging /1,2/. The full history of a transformation was gained by tracking the electron image intensity with photomultiplier and storage oscilloscopes (space/time resolution 100 nm/3 ns) /3/. In order to avoid radiation damage by the probing electron beam to detector and specimen, the beam is pulsed in this continuous mode of time-resolved TEM,too.Short events ( <2 μs) are followed by illuminating with an extended single electron pulse (fig. 1c)

Optical Properties and Phenomenological Theory of Ferri-Ferri Phase Transitions in Antiferroelectric Liquid Crystals

1997 ◽  
Vol 7 (12) ◽  
pp. 1817-1828 ◽  
Author(s):  
P. Gisse ◽  
M. Sidir ◽  
V. L. Lorman ◽  
R. Farhi ◽  
J. Pavel ◽  
...  
Keyword(s):  
Optical Properties ◽  
Phase Transitions ◽  
Liquid Crystals ◽  
Phenomenological Theory ◽  
Antiferroelectric Liquid Crystals

HIGH RESOLUTION CALORIMETRIC STUDIES AT PHASE TRANSITIONS OF ALKYLCYANOBIPHENYL LIQUID CRYSTALS CONFINED TO SUBMICRON SIZE CYLINDRICAL CAVITIES

1995 ◽  
Vol 09 (18n19) ◽  
pp. 2247-2283 ◽  
Author(s):  
DANIELE FINOTELLO ◽  
GERMANO S. IANNACCHIONE
Keyword(s):  
Phase Transitions ◽  
Liquid Crystals ◽  
High Resolution ◽  
Specific Heat ◽  
Pore Wall ◽  
Isotropic Phase ◽  
First Order ◽  
Smectic A ◽  
Nematic Director ◽  
Scalar Order Parameter

We review results of a high resolution systematic study of the specific heat for alkyl-cyanobiphenyl liquid crystals confined to the 0.2µm diameter cylindrical pores Anopore membranes. The nematic director alignment at the pore wall is varied from homeotropic to tangential by pore surface treatment. Several phenomena are uncovered by these studies which probed the weakly first order nematic to isotropic, the continuous smectic-A to nematic and the first order smectic-A to isotropic phase transitions. The specific heat is strongly dependent on the nematic director configuration, and confinement effects are remarkably distinct according to the order of the phase transition. The influence of elastic distortions and surface ordering and disordering effects are evident. Despite considerable departures from bulk behavior with regards to specific heat peaks size, rounding and width, and transition temperature shifts, a bulk-like critical behavior appears to be retained. The formation of smectic translational order within the pores is hindered for those liquid crystals that also possess a nematic phase. The average scalar order parameter temperature dependence is extracted from the specific heat results using a simplified Landau-de Gennes type of model, and is shown to be consistent with nuclear magnetic resonance results.

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