Ultrafast Photoionization Induced Proton Transfer Dynamic in Phenol-Amide Cation Complex

• Main Authors: Wu,Jun-Yi, 吳俊毅
• Other Authors: Cheng,Po-Yuan
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/yq3yud

碩士 === 國立清華大學 === 化學系 === 105 === 　　We report studies of ultrafast proton transfer (PT) reaction of phenol-N-methylformamide(PhOH-NMF) and phenol-N,N-dimethylformamide (PhOH-DMF) cation complexes by using femtosecond pump-probe photoionization-photofragmentation spectroscopy (fs-PIPF). Neutral PhOH-NMF and PhOH-DMF complexes prepared in a free jet are photoionized by femtosecond [1+1] resonance-enhanced multiphoton ionization via S1 state, and the subsequent dynamics occurring in the cations is probed by delayed pulses that result in ion fragmentation. The observed probe-wavelength dependence of the transients are consistent with a spectral evolution from the initial non-PT to final PT states. The combination of experimental results and DFT calculations suggest that a low barrier is present along [PhOH-NMF]+ cation proton transfer reaction coordinate. There are three distinct time scales in [PhOH-NMF]+ experiments : τ_1≈0.23 ps is assigned to an initial wave-packet motion, τ_2=3 ps~18 ps is assigned to the proton transfer, and τ_3=40ps~81 ps is attributed to to complex isomerization. The experiments revealed that PT in [PhOH-DMF]+ cation also proceeds in three distinct steps: τ_1≈0.3 ps an initial wave-packet motion, followed by a slower relaxation τ_2≈2 ps and a final step τ_3=15ps~17 ps of complex isomerization.