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Ultrafast optical response of IR‐treated polyacrylonitrile films
Author(s) -
Zhuravleva Tatyana S.,
Kovalenko Sergey A.,
Lozovik Yuri E.,
Matveets Yuri A.,
Farztdinov Vadim M.,
Dobryakov Alexander L.,
Nazarenko Andrey V.,
Zemtsov Lev M.,
Kozlov Vladimir V.,
Karpacheva Galina P.,
Marowsky Gerd
Publication year - 1998
Publication title -
polymers for advanced technologies
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.61
H-Index - 90
eISSN - 1099-1581
pISSN - 1042-7147
DOI - 10.1002/(sici)1099-1581(1998100)9:10/11<613::aid-pat825>3.0.co;2-j
Subject(s) - materials science , polyacrylonitrile , femtosecond , ultrashort pulse , relaxation (psychology) , excited state , infrared , photoexcitation , vibrational energy relaxation , picosecond , photochemistry , analytical chemistry (journal) , optics , molecular physics , atomic physics , laser , polymer , chemistry , physics , psychology , social psychology , chromatography , composite material
An ultrafast photoinduced optical response of infrared (heat) treated polyacrylonitrile films (PAN‐IR) was studied by a femtosecond pump–supercontinuum probe technique in the energy region of 1.6 – 3.2 eV. Two types of films were used corresponding to 600°C (1st) and to 700°C (2nd) heating. The samples were excited by optical pulses with a duration of 50 fsec and energy of ħω pump = 2.34 eV. The temporal evolution of the photoinduced response is characterized by two relaxation times τ 1 and τ 2 . For the 1st film type, the spectral dependence of the ultrafast relaxation time shows nonmonotonous behavior, it decreases from τ 1 ≈ 170 fsec to 70 fsec at 1.6 < ħω probe < 1.9 eV and increases from τ 1 ≈ 80 fsec to 140 fsec at 1.9 < ħω probe < 3.2 eV. The spectral region1.6–1.95 eV corresponds to photoinduced darkening while the region 1.95–3.2 eV corresponds to photoinduced bleaching. For the 2nd film type, only photoinduced bleaching is observed, and the ultrafast relaxation time decreases monotonously from τ 1 ≈ 200 fsec to τ 1 ≈ 70 fsec. The second relaxation time τ 2 is of ∼1 psec for both types of films. © 1998 John Wiley & Sons, Ltd.