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Digital archive of theses discussed at the University of Pisa

 

Thesis etd-09202007-122100


Thesis type
Tesi di dottorato di ricerca
Author
Amirkhani, Masoud
email address
masoud.amirkhani@gmail.com
URN
etd-09202007-122100
Thesis title
Laser spectroscopy studies of relaxation dynamics in polymers
Academic discipline
FIS/01
Course of study
FISICA
Supervisors
Relatore Prof. Leporini, Dino
Relatore Prof. Torre, Renato
Relatore Prof. Lugarà, Pietro Mario
Relatore Prof. Tonelli, Mauro
Keywords
  • Laser spectroscopy
  • Polymer
  • Relaxation
  • Second harmonic generation
  • Transient grating
Graduation session start date
04/05/2007
Availability
Withheld
Release date
04/05/2047
Summary
Polymer molecular systems are complicated and difficult to study, even in this modern age. Nowadays, there is big effort to understand mechanical and electrical behavior of these systems and many experimental methods are developed for this reason. Laser spectroscopy techniques are excellent methods to study fast and slow dynamics of the complicated polymeric systems. In our present work we used two different laser spectroscopic methods to study the plexiglass polymers. First Second Harmonic Generation (SHG) that deals with nonlinear optical properties of guest-host polymer. In this method, initially a nonlinear system is created.The evaluation of this nonlinearity
is coupled to the physical properties of the guest-host polymer. So this evaluation gives us important informations on mobility of the chain and charge treatment in the system. Second method is Transient Grating (TG) that is very powerful optoacoustic technique. In a TG experiment, the sample is excited by two spatially crossed and time coincident laser pulses producing an interference pattern. This spatially modulated excitation creates
high frequency acoustic wave due to thermal and electrostriction effect. This technique gives information on sound velocity, acoustic damping time and thermal diffusion.
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