偶氮苯染料在溶液與高分子聚合薄膜中的光致順反異構化動力學研究

Abstract

在本論文中，我們利用飛秒時間解析吸收光譜量測分析技術，研究偶氮苯染料Disperse Red 19在溶液與高分子聚合薄膜中的超快光致順反異構化動力行為。利用非共線性光參數放大器所產生之寬頻可見光波段的短脈衝作為激發－探測光源，我們可同時觀測激發態電子弛緩過程與分子振動行為。根據量測結果，DR19在溶液與高分子聚合薄膜中皆以∼100 fs的時間尺度脫離Franck-Condon能態，在溶液與高分子聚合薄膜中的激發態弛緩時間分別約為0.63 ps與0.84 ps，而高振動能的基態分子在溶液與高分子聚合薄膜中回到低振動能態的弛緩時間分別為2.55 ps與4.43 ps，藉此時間差異可推測DR19在結構緩解過程中會受到周遭分子環境的影響。

The photoisomerization of 4’-[(N,N-Dihydroxyethyl)amino]-nitroazobenzene (Disperse Red 19) in solution and in polymer film are investigated by femtosecond time-resolved absorption spectroscopy. Using broadband sub-10 fs visible pulses, the dynamics of electronic relaxation and molecular vibrations are observed in both samples. The motion of a wavepacket in the excited state out of the Franck-Condon state occurs on the time scale of ~100 fs. The excited state relaxation occurs with time constant of 0.63 ps in solution and 0.84 ps in polymer films. For a solution and a polymer film, the vibrational cooling in the ground state proceeds are 2.55 ps and 4.43 ps, respectively, suggesting that the isomerization dynamics are sensitive to the molecular environments. To the best of our knowledge, this work is the first experimental observation for the ultrafast processes of DR19 in different molecular environments.