Luminescence from trans-Polyacetylene Degraded by Laser Irradiation
Very recently we have experimentally investigated an effect on trans-(CH)x of irradiation with intense laser light of more than 120 mW [1,2]. It was found that: (1) An initial effect of irradiation with intense laser light is the remarkable changes of the Raman line shapes of the C-C and C=C stretching modes,which are always accompanied by the increment of the background intensity. (2) Upon further irradiation,the background intensity enhances drastically and finally saturates at high-intensity levels. The change of the background intensity under irradiation can be described in terms of (i) an initial slow exponential increase with a time-constant 1/γ1, (ii) a fast exponential increase after a characteristic time tc, and (iii) saturation. (3) The quantity γ1.t (~0.54) is almost independent of the experimental conditions and samples used. (4) The new luminescence in stage (iii), consists of the several bands with the peak-energy spacing of 1200 ~1400 cm−1 and exhibits the unusual exciting-energy dependence that each band shifts with the laser frequency like a first-order Raman spectrum (see Fig.1). (5) The luminescence band is quite sensitive to exposure to air or oxygen,resulting in a disappearance of the band structure, i.e.., a single-peaked luminescence band which is less dependent upon the exciting-energy.
KeywordsLaser Frequency Luminescence Band Background Intensity Streak Camera Exciting Energy
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